Add some headings to repo views (#22869)

* Add role heading level 1 to username/repo title.
* Copy behaviour of Releases to some other views.

Contributed by @forgejo.

![Screenshot with
h2](https://user-images.githubusercontent.com/5055343/218287363-dfae9ab2-7297-4367-ab64-ab141506e131.png)
![Screenshot with former
div](https://user-images.githubusercontent.com/5055343/218287419-77d0ed56-935d-492f-b3ed-71051d169ba8.png)

Co-authored-by: delvh <leon@kske.dev>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

templates/repo/header.tmpl

@@ -3,7 +3,7 @@
 	<div class="ui container">
 		<div class="repo-header">
 			<div class="repo-title-wrap df fc">
-				<div class="repo-title">
+				<div class="repo-title" role="heading" aria-level="1">
 					{{$avatar := (repoAvatar . 32 "mr-3")}}
 					{{if $avatar}}
 						{{$avatar}}

templates/repo/issue/navbar.tmpl

@@ -1,4 +1,4 @@
-<div class="ui compact left small menu">
+<h2 class="ui compact small menu header">
 	<a class="{{if .PageIsLabels}}active {{end}}item" href="{{.RepoLink}}/labels">{{.locale.Tr "repo.labels"}}</a>
 	<a class="{{if .PageIsMilestones}}active {{end}}item" href="{{.RepoLink}}/milestones">{{.locale.Tr "repo.milestones"}}</a>
-</div>
+</h2>