[docs] Missing Install Instructions for Gitea/Forgejo

[adambkaplan]

The Pipelines as Code documentation does not have explicit instructions for Gitea or its "successor" hard fork, Forgejo. However, based on several issues in this repo it is clear that some support/capabilities for these SCM providers are available.

See also:

• break gitea_test.go #2097
• Forgejo - User %s is not allowed to trigger CI via pull_request on this repo. #2103
• Add unit tests for pkg/provider/gitea/parse_payload.go #2146

[chmouel]

it's not officially supported yet...

[adambkaplan]

That's fair. I notice many open source projects are reluctant to create documentation unsupported/in progress features.

I personally don't love this - it inhibits experimentation and causes potential adopters to turn away if they wrongly believe their requirement is not feasible. I'd rather see projects document experimental/unsupported features as "in progress", "alpha", etc., with plenty of notice that the feature may change in breaking ways.