docs: Update README.md (#3019)

## Description

Added necessary `https://` prefix to two links in main README.md to
avoid 404s.

## Breaking Changes

None - just README doc changes.

## Change checklist

- [ ] Self-review.
- [ ] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.
- [ ] Tests if relevant. (not relevant to this PR)
- [ ] All breaking changes documented. (not relevant to this PR)

Author: robsyme

README.md

@@ -159,8 +159,8 @@ Unless you explicitly state otherwise, any contribution intentionally submitted
 [iroh-blobs]: https://github.com/n0-computer/iroh-blobs
 [iroh-gossip]: https://github.com/n0-computer/iroh-gossip
 [iroh-docs]: https://github.com/n0-computer/iroh-docs
-[iroh-willow]: github.com/n0-computer/iroh-willow
-[iroh-doctor]: github.com/n0-computer/iroh-doctor
+[iroh-willow]: https://github.com/n0-computer/iroh-willow
+[iroh-doctor]: https://github.com/n0-computer/iroh-doctor
 [willow protocol]: https://willowprotocol.org
 [iroh-ffi]: https://github.com/n0-computer/iroh-ffi
 [iroh-yt-video]: https://www.youtube.com/watch?v=RwAt36Xe3UI_