Refactor VLS implementation, expose VLS settings and various new features

[tommasongr]

This refactor adds numerous new features, stability improvements and adds up on code quality. Various comments have been added to the code for better explaination of what is going on. I hope others may find them usefull.

What's going on:

NEW

• Exposed VLS settings for both Global and per Project
• Added a new Information Sidebar
• Updated the version of VLS (0.7.2)
• Added informative notifications
• Added new commands for the extension
• Added a Clip for scaffolding a Vue file with POSTCSS

IMPROVED

• Improved general stability and maintanability with better structure and comments
• Polished the main extension object
• Polished the VueLanguageClient class
• Uniformed all the logs, notifications and alerts
• Polished the syntax definition

DOCS

• Improved the general quality and structure of the README
• Add a new Help section with some troubleshooting information