Fix markdown rendering in milestone content (#15056)

- Add missing markdown class for rendered markdown.
- Increase font size of milestone name in list.

Fixes: #15046

templates/repo/issue/milestone_issues.tmpl

@@ -4,8 +4,8 @@
 	<div class="ui container">
 		<div class="ui three column stackable grid">
 			<div class="column">
-				<h3>{{.Milestone.Name}}</h3>
-				<div class="content">
+				<h1>{{.Milestone.Name}}</h1>
+				<div class="markdown content">
 					{{.Milestone.RenderedContent|Str2html}}
 				</div>
 			</div>

templates/repo/issue/milestones.tmpl

@@ -43,7 +43,7 @@
 		<div class="milestone list">
 			{{range .Milestones}}
 				<li class="item">
-					{{svg "octicon-milestone"}} <a href="{{$.RepoLink}}/milestone/{{.ID}}">{{.Name}}</a>
+					{{svg "octicon-milestone" 16 "mr-2"}} <a href="{{$.RepoLink}}/milestone/{{.ID}}">{{.Name}}</a>
 					<div class="ui right green progress" data-percent="{{.Completeness}}">
 						<div class="bar" {{if not .Completeness}}style="background-color: transparent"{{end}}>
 							<div class="progress"></div>
@@ -80,7 +80,7 @@
 						</div>
 					{{end}}
 					{{if .Content}}
-						<div class="content">
+						<div class="markdown content">
 							{{.RenderedContent|Str2html}}
 						</div>
 					{{end}}

web_src/less/_repository.less

@@ -1167,6 +1167,7 @@
       > a {
         padding-top: 5px;
         padding-right: 10px;
+        font-size: 1.5rem;
         color: var(--color-text);
 
         &:hover {