Mention that Codidact is open source at https://codidact.com/contact

[matkoniecz]

Is your feature request related to a problem? Please describe.
AFAIK Codidact was supposed to be an open source project, but there is no info about this at https://codidact.com/contact - it looks like something put by company with millions in funding

Describe the solution you'd like
Put link to repo at https://codidact.com/contact

Describe alternatives you've considered
I may be wrong - maybe I confused Codidact with some other project and it is $$$-funded, not a community project created after StackExchange owners started harassing unpaid contributors?

Additional context
I know that it is wrong repo, but seems the closest - see #82