Support Gitea Service

[operatorequals]

Gitea is a self-hostable Modern Git Service. It shares many features with Gitlab, Github and the rest, such as HTTP raw file download. Thous it can be supported by httpimport

A gitea_repo can be implemented by formatting URLs such as the one below (taken from Gitea's Swagger page):

https://try.gitea.io/test/test/raw/branch/master/README.md