Banner about the upcoming TLS 1.2 enforcement (#8012)

* Quick banner for the upcoming TLS 1.2 enforcement.

* Variable for the background color.

* Aligned the banner text with the blog post.

Author: agr

src/Bootstrap/dist/css/bootstrap-theme.css

@@ -226,6 +226,10 @@ body {
   &.banner-notice {
     background: @alert-info-bg;
   }
+
+  &.banner-info {
+    background: @info-bg;
+  }
 }
 
 .alert {

src/Bootstrap/less/theme/base.less

@@ -41,7 +41,7 @@
       font-size: 14px;
 
       .tag-node {
-        background-color: #fff4ce;
+        background-color: @info-bg;
         padding: 13px; 
         text-align: left;
 

src/Bootstrap/less/theme/modals.less

@@ -36,7 +36,7 @@
     }
 
     .status-degraded {
-        background-color: #FFF4CE;
+        background-color: @info-bg;
 
         .ms-Icon {
             color: orange;

src/Bootstrap/less/theme/page-status.less

@@ -873,3 +873,5 @@
 @dl-horizontal-breakpoint:    @grid-float-breakpoint;
 //** Horizontal line color.
 @hr-border:                   @gray-lighter;
+
+@info-bg:                     #fff4ce;

src/Bootstrap/less/variables.less

@@ -8,6 +8,18 @@
     var rawErrorMessage = TempData.ContainsKey("RawErrorMessage") ? TempData["RawErrorMessage"].ToString() : null;
 }
 
+<div class="container-fluid banner banner-info text-center">
+    <div class="row">
+        <div class="col-sm-12">
+            <i class="ms-Icon ms-Icon--Warning" aria-hidden="true"></i>
+            <span>
+                NuGet.org will permanently <a href="https://devblogs.microsoft.com/nuget/nuget-org-will-permanently-remove-support-for-tls-1-0-and-1-1-on-june-15th/">
+                remove support</a> for TLS 1.0 and 1.1 on June 15th. Please ensure that your systems use TLS 1.2.
+            </span>
+        </div>
+    </div>
+</div>
+
 @if (!string.IsNullOrWhiteSpace(Config.Current.WarningBanner))
 {
     <div class="container-fluid banner banner-bright text-center">