Parse manifest of VSCode extensions and OpenVSX

[pombredanne]

Some research needed.

• there are likely some VS Code extension metadata (in addition to a package.json)
• both VSCode upstream and OpenVSX have likely formats for these

[laishettikarthik-tech]

Hi @pombredanne — I'd like to work on this. A few questions before I start:

1. Is the target the .vsix package format (a zip with extension.vsixmanifest
   • package.json inside), or just the raw package.json from the extension
     source?
2. Should this follow the existing PackageData dataclass pattern used by
   other package format parsers in scancode?
3. For OpenVSX — are you thinking of parsing their REST API response format,
   or the on-disk .vsix format (which is the same as VSCode's)?

Happy to do the research and prototype a parser once the scope is clearer.