Add support for the new sublime-syntax file

[GianlucaGuarini]

• This PR improves massively the syntax highlighting for sublime text users using the new .sublime-syntax format
• It updates the Riot.js icon
• It changes the LICENSE of this project to MIT
• It removes all the old .tmLanguage|json files

Side note: We can backup the old syntax files in a separate legacy branch moving forward for Riot.js 4.

Preview in Sublime Text