Add appearance section in settings (#17433)

* Add appearance section in settings

* Fix lint

* Fix lint

* Apply suggestions from code review

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

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

templates/user/settings/account.tmpl

@@ -130,44 +130,6 @@
 			</form>
 		</div>
 
-		<h4 class="ui top attached header">
-			{{.i18n.Tr "settings.manage_themes"}}
-		</h4>
-		<div class="ui attached segment">
-			<div class="ui email list">
-				<div class="item">
-					{{.i18n.Tr "settings.theme_desc"}}
-				</div>
-
-			<form class="ui form" action="{{.Link}}/theme" method="post">
-				{{.CsrfTokenHtml}}
-					<div class="field">
-						<label for="ui">{{.i18n.Tr "settings.ui"}}</label>
-						<div class="ui selection dropdown" id="ui">
-							<input name="theme" type="hidden" value="{{.SignedUser.Theme}}">
-							{{svg "octicon-triangle-down" 14 "dropdown icon"}}
-							<div class="text">
-								{{range $i,$a := .AllThemes}}
-									{{if eq $.SignedUser.Theme $a}}{{$a}}{{end}}
-								{{end}}
-							</div>
-
-							<div class="menu">
-							{{range $i,$a := .AllThemes}}
-								<div class="item{{if eq $.SignedUser.Theme $a}} active selected{{end}}" data-value="{{$a}}">
-									{{$a}}
-								</div>
-							{{end}}
-							</div>
-						</div>
-					</div>
-
-				<div class="field">
-					<button class="ui green button">{{$.i18n.Tr "settings.update_theme"}}</button>
-				</div>
-			</form>
-			</div>
-		</div>
 		<h4 class="ui top attached error header">
 			{{.i18n.Tr "settings.delete_account"}}
 		</h4>