Update JS dependencies and webpack (#14118)

* Update JS dependencies

- Update all JS dependencies
- Adapt webpack config for version 5
- Update to Less 4.0, adapting usage of removed mixin syntax
- Enable new ESLint rules and fix discovered issues

* update license-webpack-plugin to fix missing licenses

* update license-webpack-plugin once more to get webpack into the license output

* switch to license-checker-webpack-plugin again for performance

* update deps again

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

web_src/less/_form.less

@@ -236,7 +236,7 @@ textarea:focus,
 .user.signin,
 .user.signup {
   @input-padding: 200px;
-  #create-page-form;
+  #create-page-form();
 
   form {
     width: 700px !important;
@@ -273,7 +273,7 @@ textarea:focus,
   &.new.repo,
   &.new.migrate,
   &.new.fork {
-    #create-page-form;
+    #create-page-form();
 
     form {
       .dropdown .text {