contribution guide link is to a different project

[Caesar Schinas]

The "contribution guide" link in the readme goes to https://xplorer.space/docs/community/Contributing. I'm not sure if this is intentional but, since there's no apparent relationship between the two projects, it would be better for this project to have its own contribution guide.

Thanks for the cool project by the way, I'm looking forward to contributing once I familiarise myself with the codebase! :-)

[farfromrefuge]

@caesar thanks I actually copied their readme as a base ;)