Preparation for integration

[lextm]

Like discussed in #279 I will start to send pull requests to prepare the integration of esbonio with other extensions.

This initial one contains two changes,

1. Changed the language ID so that it matches other extensions.
2. Added some new code to detect if esbonio Python package has been installed. If not, it prompts the user to install it.

There are many more to come, and I will keep each pull request as small as possible for you to review.

[alcarney]

Thanks for this!

However, I don’t think fe879c5 is necessary as there is already code in src/lsp/server.ts that handles installation and upgrades to the server - could you remove it?

[lextm]

Removed.