feat(renovate): support SHA-pinned URLs in Renovate preset (#21)

## Summary
- Update Renovate shared preset regex to match SHA-pinned
`raw.githubusercontent.com` URLs with version comments (e.g., `#
v0.3.0`)
- Update README to document SHA-pinned URL pattern for consuming repos

## Test plan
- [ ] Verify Renovate preset regex matches SHA-pinned URLs in
`mise.toml`
- [ ] Verify Renovate can detect and update pinned versions

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger