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/user/dashboard/issues.tmpl

@@ -82,7 +82,7 @@
 						<div class="ui 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 or (eq .SortType "latest") (not .SortType)}}active{{end}} item" href="{{$.Link}}?type={{$.ViewType}}&repos=[{{range $.RepoIDs}}{{.}}%2C{{end}}]&sort=latest&state={{$.State}}&q={{$.Keyword}}">{{.i18n.Tr "repo.issues.filter_sort.latest"}}</a>