Add GitHub workflow

[atoomic]

also provides some badges on the mkdn page.

once merged you could check the Actions tab and very commit/PR will be smoked on linux, windows, macos

sample runs: https://github.com/atoomic/File-pushd/actions

[coveralls]

Coverage remained the same at 96.491% when pulling a79238d on atoomic:gh-workflow into 9566e9c on dagolden:master.

[xdg]

I appreciate the attempt at modernizing. However, on reflection, I don't want to make these sort of meta changes for a module that I'm minimally involved in.