Add automatic JS license generation (#11810)

* Add automatic JS license generation

Removed librejs file and replaced it with a plaintext file that is built
from all JS dependencies that are included in the webpack build. It does
not cover the few remaining statically vendored files and fomantic is
added manually because it's not yet in the webpack build process.

Fixes: https://github.com/go-gitea/gitea/issues/11630

* fix lint

* remove jslicense, we're not librejs compatible any more

* remove license.txt test as it depens on absent files

* small optimization

* trailing comma

* localize and capitalize the word 'licenses'

* reduce text to just 'Licenses'

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

options/locale/locale_en-US.ini

@@ -20,6 +20,7 @@ user_profile_and_more = Profile and Settings…
 signed_in_as = Signed in as
 enable_javascript = This website works better with JavaScript.
 toc = Table of Contents
+licenses = Licenses
 
 username = Username
 email = Email Address