Comment box tweaks and SVG dropdown triangles (#13376)

* Comment box tweaks and SVG dropdown triangles

- Change all dropdown triangles to SVG
- Bring inline review comment box closer to regular comment boxes
- Enhance arc-green checkbox contrast
- Minor reaction tweaks
- Flexbox the diff file header

* remove a border

* fix type marker in arc-green

* add small code padding

* fix position regression and remove useless rules

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

templates/explore/repo_search.tmpl

@@ -3,7 +3,7 @@
     <div class="ui right dropdown type jump item">
 		<span class="text">
 			{{.i18n.Tr "repo.issues.filter_sort"}}
-                <i class="dropdown icon"></i>
+                {{svg "octicon-triangle-down" 14 "dropdown icon"}}
 		</span>
         <div class="menu">
             <a class="{{if eq .SortType "newest"}}active{{end}} item" href="{{$.Link}}?sort=newest&q={{$.Keyword}}&tab={{$.TabName}}">{{.i18n.Tr "repo.issues.filter_sort.latest"}}</a>

templates/explore/search.tmpl

@@ -3,7 +3,7 @@
 	<div class="ui right dropdown type jump item">
 		<span class="text">
 			{{.i18n.Tr "repo.issues.filter_sort"}}
-			<i class="dropdown icon"></i>
+			{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 		</span>
 		<div class="menu">
 			<a class="{{if eq .SortType "newest"}}active{{end}} item" href="{{$.Link}}?sort=newest&q={{$.Keyword}}&tab={{$.TabName}}">{{.i18n.Tr "repo.issues.filter_sort.latest"}}</a>