Allow to override default language map

[nchursin]

Hi!

I added an ability to override the default language mapping, so anyone can use the extension for any language that is not supported officially but can be handled by supported prettifiers.

For example, this adds an ability to handle Apex as C instead of Java. This might be useful, as uncrustify has problems with Java class indentation

[LaurentTreguier]

Apart from the comments I made, I think it's a pretty good idea ! This will probably help some other people :+1:

[nchursin]

Fixed the issues you mentioned

It might be a good idea to have an .editorconfig file in the repo to avoid indentation problems and some other style problems in future :slightly_smiling_face: I'm totally with you on maintaining a consistent style

[LaurentTreguier]

Vscode usually just auto-detects indentation, so I was simply relying on that