Generate language meta data

[msujew]

Closes #168

Adds a dedicated LanguageMetaData service to each language.

export interface LanguageMetaData {
    languageId: string;
    extensions: string[];
}

[dhuebner]

Great! Exactly what I need. We need to decide about having a leading . or not.
I tend to prefer the no-dot solution

[pluralia]

Leading . are redundant, however, it's nice to have it to support the association: "if a string starts with ., it's an extension". It highlights extensions over all other metadata.

[msujew]

I prefer the . variation as well, since path.extname will return the ext with a .. So we don't have to do transformations on that.

[spoenemann]

In this case I'd rather use a plain object than a class.

[msujew]

I see, that makes sense. Should the object this be generated into a meta-data.ts file, or should it be build in the generated injection module? like this:

LanguageMetaData: () => ({
    languageId: 'id',
    extensions: ['.id']
})

[spoenemann]

Exporting a const for it could be useful so you can access it directly in your language implementation. But it could be in the generated/module.ts instead of a new file to keep the number of generated files low.

[msujew]

Alright, yeah I agree with that.

[spoenemann]

Shall we name this property fileExtensions for clarity? "extensions" is quite generic.