Adding stolon (cloud native postgres ha) links/examples.

[sgotti]

Stolon comes with its own kubernetes examples.

Are you interested in a PR with some links to them in the README or would you prefer an adapted copy of the statefulset/petset example?

[sgotti]

bump. We just released stolon v0.5.0 with a big rework and a lot of new features (https://github.com/sorintlab/stolon/releases/tag/v0.5.0).

I think it'll be good if atomicdb can provide another postgres ha solution used by different organizations (it's not a governor/patroni clone in go but it has a much different architecture and better consistency than other alternatives).