Filter for default-branch selection (go-gitea#29388)

Filter for default-branch selection (fixes go-gitea#4751)

before:

![image](https://github.com/go-gitea/gitea/assets/72873130/dcae266d-2e04-41bf-8739-64a85c9007f6)

after:

![image](https://github.com/go-gitea/gitea/assets/72873130/5f27c0a7-1d30-4ccd-b4bb-6c34fff1b79f)

---------

Co-authored-by: silverwind <me@silverwind.io>

templates/repo/settings/branches.tmpl

@@ -16,7 +16,7 @@
 					{{.CsrfTokenHtml}}
 					<input type="hidden" name="action" value="default_branch">
 					{{if not .Repository.IsEmpty}}
-						<div class="ui dropdown selection gt-f1 gt-mr-3 tw-max-w-96">
+						<div class="ui dropdown selection search gt-f1 gt-mr-3 tw-max-w-96">
 							{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 							<input type="hidden" name="branch" value="{{.Repository.DefaultBranch}}">
 							<div class="default text">{{.Repository.DefaultBranch}}</div>