Remove unnecessary returns in cors common

[FIX] file upload broken when running in subdirectory https://github.com…

fix file upload issue when running in subdirectory https://github.com/RocketChat/Rocket.Chat/issues/6679

* Add ESLint rule `prefer-template`

* Add ESLint rule `template-curly-spacing `

* ESLint ignore rocketchat-livechat/assets/rocket-livechat.js

* Add ecmascript package to all packages

* Use ecmascript package for server and client on saml package

* Fix compilation