CI: explicitly build for old Apple chips

Github's CI infrastructure seems to have updated to new apple chips.
Thus, by default, maturin compiles packages for new apple chips when run
on macos. This commit makes sure we still also run cross compilation for
old (intel) Apple hardware.

Allow re-running `release` action.

Merge pull request #44 from bamler-lab/issue-41

(branch name is misleading, it should have been called issue-43)

Bump version to 0.3.4

Merge pull request #42 from bamler-lab/issue-40

Reduce minimum required numpy version from 1.19 to 1.16

Fix "release" CI action

Bump version to 0.3.1

Merge pull request #22 from bamler-lab/v0.3

v0.3

Run `poetry update`

Update third party licenses