Style and template tweaks (#13828)

* Style and template tweaks

- Get red and green buttons on arc green closer to base theme
- EasyMDE adjustments, toolbar and focus border
- Fix header on 404 repo page
- Tweaks to frontpage search, add 'Create Repo' button
- Fix misaligned box headers
- Fix pagination on arc-green
- Fix background and footer on explore and repo search

* better fix for header button alignment

* add label hover for reactions

templates/user/dashboard/issues.tmpl

@@ -77,7 +77,7 @@
 							</div>
 						</form>
 					</div>
-					<div class="column right aligned">
+					<div class="column right aligned df ac je">
 						<!-- Sort -->
 						<div class="ui dropdown type jump item">
 							<span class="text">