Add small info about extension.

[Kapelianovych]

I have add small doc about extension, some required fields for publishing.

[Kapelianovych]

Add compile script. Fix #210.
Change name of package - because vsce tool does not recognize scopes.
Now users will be able to compile and install extension. Fix #228.

Prerequisites: for compiling extension yarn must be locally installed. Because vsce have troubles with different npm versions.

yarn run compile
code --install-extension hegel-language-server-0.0.43.vsix

And use :)