Improve some modal action buttons (#24289)

Follow #24097 and #24285

And add a devtest page for modal action button testing.
http://localhost:3000/devtest/fomantic-modal

Now the `modal_actions_confirm.tmpl` could support: green / blue /
yellow positive buttons, the negative button is "secondary".

ps: this PR is only a small improvement, there are still a lot of
buttons not having proper colors. In the future these buttons could be
improved by this approach.

These buttons could also be improved according to the conclusion of
#24285 in the future.



![image](https://user-images.githubusercontent.com/2114189/233847773-a6d6b29b-7b5c-490e-8425-40dfd0ad2529.png)


And add GitHub-like single danger button (context:
https://github.com/go-gitea/gitea/issues/24285#issuecomment-1519100312)


![image](https://user-images.githubusercontent.com/2114189/233891566-055d7611-894d-4d5a-baf5-f6369180bf8d.png)

---------

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

templates/repo/settings/lfs.tmpl

@@ -36,7 +36,7 @@
 		</table>
 		{{template "base/paginate" .}}
 		{{range .LFSFiles}}
-			<div class="ui gitea-confirm-modal modal" id="delete-{{.Oid}}">
+			<div class="ui g-modal-confirm modal" id="delete-{{.Oid}}">
 				<div class="header">
 					{{$.locale.Tr "repo.settings.lfs_delete" .Oid}}
 				</div>
@@ -46,14 +46,10 @@
 					</p>
 					<form class="ui form" action="{{$.Link}}/delete/{{.Oid}}" method="post">
 						{{$.CsrfTokenHtml}}
-						<div class="actions">{{/* TODO: Convert to base/modal_actions_confirm */}}
-							<button class="ui basic cancel inverted button">{{$.locale.Tr "settings.cancel"}}</button>
-							<button class="ui basic inverted yellow button">{{$.locale.Tr "modal.yes"}}</button>
-						</div>
+						{{template "base/modal_actions_confirm" (dict "locale" $.locale "ModalButtonColors" "yellow")}}
 					</form>
 				</div>
 			</div>
 		{{end}}
 	</div>
-</div>
 {{template "repo/settings/layout_footer" .}}