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>

templates/user/dashboard/milestones.tmpl

@@ -49,7 +49,7 @@
 					<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 "closestduedate") (not .SortType)}}active{{end}} item" href="{{$.Link}}?repos=[{{range $.RepoIDs}}{{.}}%2C{{end}}]&sort=closestduedate&state={{$.State}}">{{.i18n.Tr "repo.milestones.filter_sort.closest_due_date"}}</a>

templates/user/dashboard/navbar.tmpl

@@ -11,7 +11,7 @@
 							{{if .ContextUser.Visibility.IsPrivate}}<div class="ui red tiny horizontal label">{{.i18n.Tr "org.settings.visibility.private_shortname"}}</div>{{end}}
 						</span>
 					{{end}}
-					<i class="dropdown icon"></i>
+					{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 				</span>
 				<div class="context user overflow menu" tabindex="-1">
 					<div class="ui header">