Migrate MyGet script to GH actions (#41583)

* Migrate MyGet script to GH actions to automatically build/publish the
Bootstrap NuGet package when a release is created

* Remove `-NoPackageAnalysis` flag

* Use sha-1 for jobs

---------

Co-authored-by: Jesse Mandel <jesse.mandel@jdpa.com>
Co-authored-by: Julien Déramond <juderamond@gmail.com>

nuget/MyGet.ps1

@@ -1,17 +0,0 @@
-# set env vars usually set by MyGet (enable for local testing)
-#$env:SourcesPath = '..'
-#$env:NuGet = "./nuget.exe" # https://dist.nuget.org/win-x86-commandline/latest/nuget.exe
-
-$nuget = $env:NuGet
-
-# parse the version number out of package.json
-$bsversionParts = ((Get-Content $env:SourcesPath\package.json) -join "`n" | ConvertFrom-Json).version.split('-', 2) # split the version on the '-'
-$bsversion = $bsversionParts[0]
-
-if ($bsversionParts.Length -gt 1) {
-  $bsversion += '-' + $bsversionParts[1].replace('.', '').replace('-', '_') # strip out invalid chars from the PreRelease part
-}
-
-# create packages
-& $nuget pack "$env:SourcesPath\nuget\bootstrap.nuspec" -Verbosity detailed -NonInteractive -NoPackageAnalysis -BasePath $env:SourcesPath -Version $bsversion
-& $nuget pack "$env:SourcesPath\nuget\bootstrap.sass.nuspec" -Verbosity detailed -NonInteractive -NoPackageAnalysis -BasePath $env:SourcesPath -Version $bsversion

nuget/bootstrap.nuspec

@@ -2,7 +2,7 @@
 <package xmlns="http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd">
   <metadata>
     <id>bootstrap</id>
-    <!-- pulled from package.json -->
+    <!-- pulled from release tag -->
     <version>5</version>
     <title>Bootstrap CSS</title>
     <authors>The Bootstrap Authors</authors>

nuget/bootstrap.sass.nuspec

@@ -2,7 +2,7 @@
 <package xmlns="http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd">
   <metadata>
     <id>bootstrap.sass</id>
-    <!-- pulled from package.json -->
+    <!-- pulled from release tag -->
     <version>5</version>
     <title>Bootstrap Sass</title>
     <authors>The Bootstrap Authors</authors>