Pull Request resolves #45891, #47199 and #46877 (comment).

Same as #47272 and #47273 but for 6.2 as new dev dependencies

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

• add @stylistic/eslint-plugin to get basic code style checks for javascript files back
• add eslint-plugin-cypress to check files for system tests (cypress) and fix #47199
• update eslint config to use eslint-plugin-vue
• reapply #44852 to exit on warnings
• fix existing code style errors

Testing Instructions

run npm run lint:js and npm run lint:testjs

Actual result BEFORE applying this Pull Request

basic code style (indentation, comma, semicolon) is not checked
vue files are not checked

Expected result AFTER applying this Pull Request

basic code style (indentation, comma, semicolon) is checked (again)
vue files are checked
warnings results in exit code 1

Link to documentations

Please select:

• No documentation changes for guide.joomla.org needed
• No documentation changes for manual.joomla.org needed