Allow Sourcemaps to be a array

[amcdnl]

It would be better if the source maps option would accept an array. Instead of:

sourcemaps: ./dist/bar ./out/bar

it would be:

sourcemaps:
  - ./dist/bar
  - ./out/bar

[mgaeta]

According to the docs, jobs.<job_id>.steps[*].with must be a map of string keys to string values. We'll be able to do this when GitHub Actions implement array parameters.

[amcdnl]

What about glob support? I think that would clean this up even more for me.