Support all the file types supported by Lizard

[brobeson]

The initial implementation of the extension only supports C++, but Lizard supports more languages. The extension needs to work for those, too. Known changes to the extension are:

• package.json

  "activationEvents": [
    "onLanguage:cpp"
  ],

• src/lizard.ts

  if (!['cpp'].includes(file.languageId) || file.uri.scheme !== 'file') {
    return [];
  }