Restore go-gitea#10096/go-gitea#8638 and re-fix go-gitea#15172

This PR restores the vendored and patched dropdow from go-gitea#8638. It
however, abandons the calls to `click()` using instead the default
dropdown click calls instead. This prevents the issue of the dropdown
grabbing focus permanently however, this may have negative effects on
the effect of focus on the dropdowns.

Of note, the behaviour of the template selector dropdown on the repo
creation page is slightly odd - I don't believe that this odd behaviour
is caused by this PR but rather by the feed source for this. I suspect
that the dropdown should be adding a delete button to its selection.

Fix go-gitea#15172
References: go-gitea#7057

Signed-off-by: Andrew Thornton <art27@cantab.net>

.eslintrc

@@ -2,6 +2,7 @@ root: true
 reportUnusedDisableDirectives: true
 
 ignorePatterns:
+  - /web_src/js/vendor
   - /templates/base/head.tmpl
   - /templates/repo/activity.tmpl
   - /templates/repo/view_file.tmpl

web_src/js/index.js

@@ -3,6 +3,7 @@ import './publicpath.js';
 import Vue from 'vue';
 import {htmlEscape} from 'escape-goat';
 import 'jquery.are-you-sure';
+import './vendor/dropdown.js';
 
 import ActivityTopAuthors from './components/ActivityTopAuthors.vue';
 import attachTribute from './features/tribute.js';