Merge branch 'new-branch-button-highlight' into 'master'

Add green outline to New Branch button

## What does this MR do?

Add green outline to New Branch button on issue page.

## Are there points in the code the reviewer needs to double check?

Nope.

## Why was this MR needed?

The button was not very visible.

## What are the relevant issue numbers?

fixes #18928 

## Screenshots

### Before

![before](/uploads/3bc890e249ef4c3852605a6350c05b9a/before.png)

### After

![after](/uploads/bc627902ffa7c7b4ab20ee7a269fa44f/after.png)

See merge request !5447

CHANGELOG

@@ -4,6 +4,7 @@ v 8.11.0 (unreleased)
   - Remove magic comments (`# encoding: UTF-8`) from Ruby files !5456 (winniehell)
   - Fix of 'Commits being passed to custom hooks are already reachable when using the UI'
   - Limit git rev-list output count to one in forced push check
+  - Add green outline to New Branch button !5447 (winniehell)
   - Retrieve rendered HTML from cache in one request
   - Nokogiri's various parsing methods are now instrumented
   - Make fork counter always clickable !5463 (winniehell)

app/assets/stylesheets/framework/buttons.scss

@@ -135,6 +135,15 @@
     @include btn-green;
   }
 
+  &.btn-inverted {
+    &.btn-success,
+    &.btn-new,
+    &.btn-create,
+    &.btn-save {
+      @include btn-outline($white-light, $green-normal, $green-normal, $green-light, $white-light, $green-light);
+    }
+  }
+
   &.btn-gray {
     @include btn-gray;
   }

app/views/projects/issues/_new_branch.html.haml

@@ -2,7 +2,7 @@
   .pull-right
     #new-branch{'data-path' => can_create_branch_namespace_project_issue_path(@project.namespace, @project, @issue)}
       = link_to namespace_project_branches_path(@project.namespace, @project, branch_name: @issue.to_branch_name, issue_iid: @issue.iid),
-        method: :post, class: 'btn has-tooltip', title: @issue.to_branch_name, disabled: 'disabled' do
+        method: :post, class: 'btn btn-new btn-inverted has-tooltip', title: @issue.to_branch_name, disabled: 'disabled' do
         .checking
           = icon('spinner spin')
           Checking branches