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/SUMMARY.md

@@ -16,6 +16,7 @@
     - [Broadcast and Update a Git Repository](repo/announce.md)
     - [View Git Repository Details](repo/view.md)
     - [Repository State Announcements](repo/state.md)
+  - [Reply to Issues and Patches](reply.md)
   - [Issue Management](issue/README.md)
     - [Create an Issue](issue/new.md)
     - [View an Issue By ID](issue/view.md)
@@ -32,4 +33,13 @@
     - [Apply an Open Patch](patch/apply.md)
     - [Merge an Open Patch](patch/merge.md)
     - [List Repositories Patches](patch/list.md)
-  - [Reply to Issues and Patches](reply.md)
+  - [Pull Request Management](pr/README.md)
+    - [Create a Pull Request](pr/new.md)
+    - [Update a Pull Request](pr/update.md)
+    - [View a Pull Request](pr/view.md)
+    - [List Pull Requests](pr/list.md)
+    - [Close a Pull Request](pr/close.md)
+    - [Convert to Draft](pr/draft.md)
+    - [Reopen a Pull Request](pr/reopen.md)
+    - [Mark as Applied](pr/apply.md)
+    - [Merge a Pull Request](pr/merge.md)