Examples updates (#24898)

* fix cover nav

* Improve signin visuals and alignment with that flexbox love

* rewrite cover example in flexbox

* lighten signin bg

* first pass at pricing example

* redo examples index with data file

* tighten up spacing a bit

* update navbar descriptions

* link pricing

* move that back

* property order

* Fix test errors.

* Compress pricing.png.

* add form validation example

* remove that

* rename that

* restyle and space out

* fix errors

* change order

* cleanup album css and styles

* tweak examples index

* make it a badge

* options

* improve sticky footer alignment

* redesign example index

* brand new blog layout

* start new screenshots

* new product example page a la apple

* add email field

* fix linter, remove unused blog css

* hook up feather icons to start

* redo dashboard

* fix linting

* add floating labels example

* formatting

* formatting

* lint

* fix values on select

* optional input, plus input group

* new dashboard image

* start to reboot the offcanvas example

* updated images

* new offcanvas mostly implemented

* linting

* edit description

* more description changes

* - Add vertical margin to album hero buttons for when they're stacked
- Adjust font-size and padding for pricing header and hero
- Fix checkout's stacked column margins, plus update their check/radio
markup
- Update product's utilities to be responsive
- Made blog cards somewhat responsive (needs a bit more work tbh)

* drop leading zero

* more linting

* swap empty images for holder, fix border

* dist the docs

* navbars have no margin-bottom to begin

* add css var, tweak padding for mobile

* comment headers

* nix commented out code

* nix the navbar structure for a custom one, stack it on mobile

* tweak heading button group for mobile

* Removed narrow jumbotron and justified nav examples as these are easily accomplished with new components in v4

* improve card sizing on pricing

* update and compress

docs/4.0/examples/floating-labels/floating-labels.css

@@ -0,0 +1,87 @@
+:root {
+  --input-padding-x: .75rem;
+  --input-padding-y: .75rem;
+}
+
+html,
+body {
+  height: 100%;
+}
+
+body {
+  display: -ms-flexbox;
+  display: -webkit-box;
+  display: flex;
+  -ms-flex-align: center;
+  -ms-flex-pack: center;
+  -webkit-box-align: center;
+  align-items: center;
+  -webkit-box-pack: center;
+  justify-content: center;
+  padding-top: 40px;
+  padding-bottom: 40px;
+  background-color: #f5f5f5;
+}
+
+.form-signin {
+  width: 100%;
+  max-width: 420px;
+  padding: 15px;
+  margin: 0 auto;
+}
+
+.form-label-group {
+  position: relative;
+  margin-bottom: 1rem;
+}
+
+.form-label-group > input,
+.form-label-group > label {
+  padding: var(--input-padding-y) var(--input-padding-x);
+}
+
+.form-label-group > label {
+  position: absolute;
+  top: 0;
+  left: 0;
+  display: block;
+  width: 100%;
+  margin-bottom: 0; /* Override default `<label>` margin */
+  line-height: 1.5;
+  color: #495057;
+  border: 1px solid transparent;
+  border-radius: .25rem;
+  transition: all .1s ease-in-out;
+}
+
+.form-label-group input::-webkit-input-placeholder {
+  color: transparent;
+}
+
+.form-label-group input:-ms-input-placeholder {
+  color: transparent;
+}
+
+.form-label-group input::-ms-input-placeholder {
+  color: transparent;
+}
+
+.form-label-group input::-moz-placeholder {
+  color: transparent;
+}
+
+.form-label-group input::placeholder {
+  color: transparent;
+}
+
+.form-label-group input:not(:placeholder-shown) {
+  padding-top: calc(var(--input-padding-y) + var(--input-padding-y) * (2 / 3));
+  padding-bottom: calc(var(--input-padding-y) / 3);
+}
+
+.form-label-group input:not(:placeholder-shown) ~ label {
+  padding-top: calc(var(--input-padding-y) / 3);
+  padding-bottom: calc(var(--input-padding-y) / 3);
+  font-size: 12px;
+  color: #777;
+}