Normalize all links. (#24109)

* use a trailing slash when possible
* use https when possible
* remove a few redirected links
* consistently use `https://popper.js.org/`
* fix `iconUrl` in nuget files
* change Jekyll Windows guide to the official one

docs/4.0/components/card.md

@@ -560,7 +560,7 @@ Just like with card groups, card footers in decks will automatically line up.
 
 ### Card columns
 
-Cards can be organized into [Masonry](http://masonry.desandro.com)-like columns with just CSS by wrapping them in `.card-columns`. Cards are built with CSS `column` properties instead of flexbox for easier alignment. Cards are ordered from top to bottom and left to right.
+Cards can be organized into [Masonry](https://masonry.desandro.com/)-like columns with just CSS by wrapping them in `.card-columns`. Cards are built with CSS `column` properties instead of flexbox for easier alignment. Cards are ordered from top to bottom and left to right.
 
 **Heads up!** Your mileage with card columns may vary. To prevent cards breaking across columns, we must set them to `display: inline-block` as `column-break-inside: avoid` isn't a bulletproof solution yet.
 

docs/4.0/components/dropdowns.md

@@ -10,7 +10,7 @@ toc: true
 
 Dropdowns are toggleable, contextual overlays for displaying lists of links and more. They're made interactive with the included Bootstrap dropdown JavaScript plugin. They're toggled by clicking, not by hovering; this is [an intentional design decision.](http://markdotto.com/2012/02/27/bootstrap-explained-dropdowns/)
 
-Dropdowns are built on a third party library, [Popper.js](https://popper.js.org), which provides dynamic positioning and viewport detection. Be sure to include [popper.min.js]({{ site.cdn.popper }}) before Bootstrap's JavaScript or use `bootstrap.bundle.min.js` / `bootstrap.bundle.js` which contains Popper.js.
+Dropdowns are built on a third party library, [Popper.js](https://popper.js.org/), which provides dynamic positioning and viewport detection. Be sure to include [popper.min.js]({{ site.cdn.popper }}) before Bootstrap's JavaScript or use `bootstrap.bundle.min.js` / `bootstrap.bundle.js` which contains Popper.js.
 
 If you're building our JS from source, it [requires `util.js`]({{ site.baseurl }}/docs/{{ site.docs_version }}/getting-started/javascript/#util).
 

docs/4.0/components/forms.md

@@ -672,7 +672,7 @@ While Bootstrap will apply these styles in all browsers, Internet Explorer 11 an
 
 ## Validation
 
-Provide valuable, actionable feedback to your users with HTML5 form validation–[available in all our supported browsers](http://caniuse.com/#feat=form-validation). Choose from the browser default validation feedback, or implement custom messages with our built-in classes and starter JavaScript.
+Provide valuable, actionable feedback to your users with HTML5 form validation–[available in all our supported browsers](https://caniuse.com/#feat=form-validation). Choose from the browser default validation feedback, or implement custom messages with our built-in classes and starter JavaScript.
 
 {% callout warning %}
 We **highly recommend** custom validation styles as native browser defaults are not announced to screen readers.

docs/4.0/components/navbar.md

@@ -395,7 +395,7 @@ When the container is within your navbar, its horizontal padding is removed at b
 
 ## Placement
 
-Use our position utilities to place navbars in non-static positions. Choose from fixed to the top, fixed to the bottom, or stickied to the top. **Note that `position: sticky`, used for `.sticky-top`, [isn't fully supported in every browser](http://caniuse.com/#feat=css-sticky).**
+Use our position utilities to place navbars in non-static positions. Choose from fixed to the top, fixed to the bottom, or stickied to the top. **Note that `position: sticky`, used for `.sticky-top`, [isn't fully supported in every browser](https://caniuse.com/#feat=css-sticky).**
 
 {% example html %}
 <nav class="navbar navbar-light bg-light">

docs/4.0/components/popovers.md

@@ -11,7 +11,7 @@ toc: true
 Things to know when using the popover plugin:
 
 
-- Popovers rely on the 3rd party library [Popper.js](https://popper.js.org) for positioning. You must include [popper.min.js]({{ site.cdn.popper }}) before bootstrap.js or use `bootstrap.bundle.min.js` / `bootstrap.bundle.js` which contains Popper.js in order for popovers to work!
+- Popovers rely on the 3rd party library [Popper.js](https://popper.js.org/) for positioning. You must include [popper.min.js]({{ site.cdn.popper }}) before bootstrap.js or use `bootstrap.bundle.min.js` / `bootstrap.bundle.js` which contains Popper.js in order for popovers to work!
 - Popovers require the [tooltip plugin]({{ site.baseurl }}/docs/{{ site.docs_version }}/components/tooltips/) as a dependency.
 - If building our JS from source, it [requires `util.js`]({{ site.baseurl }}/docs/{{ site.docs_version }}/getting-started/javascript/#util).
 - Popovers are opt-in for performance reasons, so **you must initialize them yourself**.

docs/4.0/components/tooltips.md

@@ -10,7 +10,7 @@ toc: true
 
 Things to know when using the tooltip plugin:
 
-- Tooltips rely on the 3rd party library [Popper.js](https://popper.js.org) for positioning. You must include [popper.min.js]({{ site.cdn.popper }}) before bootstrap.js or use `bootstrap.bundle.min.js` / `bootstrap.bundle.js` which contains Popper.js in order for tooltips to work!
+- Tooltips rely on the 3rd party library [Popper.js](https://popper.js.org/) for positioning. You must include [popper.min.js]({{ site.cdn.popper }}) before bootstrap.js or use `bootstrap.bundle.min.js` / `bootstrap.bundle.js` which contains Popper.js in order for tooltips to work!
 - If building our JS from source, it [requires `util.js`]({{ site.baseurl }}/docs/{{ site.docs_version }}/getting-started/javascript/#util).
 - Tooltips are opt-in for performance reasons, so **you must initialize them yourself**.
 - Tooltips with zero-length titles are never displayed.