Added utility function for downloading and loading models results

[KennethEnevoldsen]

Model results can now be loaded using

mteb.load_results()

This will download the results repo (on github) -- or update it if needed -- and then load then in as a dict (see docstring).

The hope is that this is the start to developing better result fetching + result downloading from MTEB. I could also imagine we could add the option to load specific model result from HF hub, push results to models card (creating a PR) etc.

Checklist

• Run tests locally to make sure nothing is broken using make test.
• Run the formatter to format the code using make lint.

[orionw]

I like this, thanks @KennethEnevoldsen. Then we can test that new changes can still load and also run some Github Actions using it.