Fix/rotate pypi creds

[glow-mdsol]

• owing to travis-ci being a bad boy we needed to rotate the credentials
• took the opportunity to move to GH actions for CI

[isparks]

Ok to merge, I see one failing CI check (CI/Build and publish) is this expected?

[glow-mdsol]

yeah, just working out the nits of the GitHub actions workflow

[glow-mdsol]

Ok, think we're good now

[isparks]

OK. Merging.