Feature: Support for Gitea

[pc-coder]

Gitea supports the creation of commit statuses via repoCreateStatus

Through this plugin, we are going to call the above URL for all the commits triggering the pipeline(triggered by gocd-build-github-pull-requests plugin).

Limitations:

1. Only PRs are supported. Since the material is filtered out based on the poller plugin-id which in our case is gocd-build-github-pull-requests plugin

[pc-coder]

PR for the same #168.