move semantic.dropdown.custom.js to webpack (#9064)

* move semantic.dropdown.custom.js to webpack

Also disabled a annoying linter rule which insisted that imports can not
contain a file extension.

Fixes: https://github.com/go-gitea/gitea/issues/8971

* reorganize web_src files and rebuild

* restart ci

.eslintrc

@@ -25,14 +25,15 @@ globals:
   Vue: false
 
 rules:
+  arrow-body-style: [0]
   camelcase: [0]
   comma-dangle: [2, only-multiline]
   consistent-return: [0]
   default-case: [0]
   func-names: [0]
+  import/extensions: [0]
   max-len: [0]
   newline-per-chained-call: [0]
-  arrow-body-style: [0]
   no-alert: [0]
   no-continue: [0]
   no-mixed-operators: [0]