This adds an api endpoint `/files` to PRs that allows to get a list of changed files. built upon #18228, reviews there are included closes https://github.com/go-gitea/gitea/issues/654 Co-authored-by: Anton Bracke <[email protected]> Co-authored-by: 6543 <[email protected]> Co-authored-by: wxiaoguang <[email protected]>