feat: support pull requests

Support for pull requests, it's not standard in NIPs yet[1] but there must be
two clients that support it to be included in NIPs, n34 is one of them.

This support:
- Create a new PR `n34 pr new`
- Update PR tip `n34 pr update`
- View a PR `n34 pr view`
- List PRs `n34 pr list`
- Add `PR` and `PR-update` kinds as roots in `NostrClient::find_root`
- Support issuing statuses for PRs
- Support GRASP PR and PR-update
- Update the docs

[1] https://github.com/nostr-protocol/nips/pull/1966

docs/pr/apply.md

@@ -0,0 +1,24 @@
+# Mark as Applied
+
+> `n34 pr apply` command
+
+**Usage:**
+```
+Usage: n34 pr apply [OPTIONS] <PR_ID> <APPLIED_COMMITS>...
+
+Arguments:
+  <PR_ID>               The open PR id to apply it
+  <APPLIED_COMMITS>...  The applied commits
+
+Options:
+      --repo <NADDR-NIP05-OR-SET>  Repository addresses
+```
+
+Creates a kind `1631` event (Applied/Merged status) for the specified PR. The PR
+must be in open status.
+
+The `APPLIED_COMMITS` field serves to inform clients about the status of
+specific commits, whether they have been applied or not. If you need to retrieve
+the list of commits from a specific point (such as the tip of the master branch)
+up to the `HEAD`, you can use the following Git command: `git log --pretty=%H
+'origin/master..HEAD'`.