appview/repo/pulls/new: 1st drafts for the new pr page
frontend-only code for the moment.
needs htmx & backend implementations.
- `new-patch.html`: for patch-based pr creation
- `new-branch.html`: for branch-based pr creation
- `new-fork.html`: for fork-based pr creation
Signed-off-by: eti <eti@eti.tf>