chore: add a release process & prepare v0.1.0

[nepinhum]

What this changes

The module had no tags, no changelog and no way to announce a breaking change.
A dependent could only track master and find out by failing to compile. So, this pr introduces:

• Release workflow - triggers on a vX.Y.Z tag and refuses to publish
  unless v.mod agrees with the tag, CHANGELOG.md has a non empty section
  for that version and the suite passes on ubuntu and macos. The changelog
  section becomes the release notes.
• examples/smoke - the example CI builds and runs.
  -Added CHANGELOG.md, Makefile

How it was checked

R against the pinned compiler, V 0.5.2 316db75:

make test V=<pinned>          # passes
make vet V=<pinned>           # exit 0 (24 missing doc warnings, pre existing)
make example V=<pinned>       # smoke ok
make example-prod V=<pinned>  # smoke ok

## Checklist

- [x] `v fmt -w .` ran
- [x] Tests pass
- [ ] A new module carries a `README.md`