Runner: Reuse/import workflows

[fregante]

Describe the enhancement

Workflows tend to grow large once you start splitting some steps to run in separate jobs. Some other workflows are inherently large because they do a lot.

In many cases, I reuse the same workflow in multiple repositories and I wish I could just import it instead of copy-pasting it and manually updating it everywhere.

Code Snippet

I wish I could just use this in a workflow file:

import:
  - use: fregante/workflows@v1
    file: webextension-deployment.yml

and this would work as if I copied the whole file.

[sindresorhus]

The biggest reason I'm currently staying on Travis CI for existing projects is that the same config for GitHub Actions is more verbose and boilerplaty. Would be nice if workflows could be reused across repos.

[MarcosCela]

This will be a game changer to manage workflows on a big org.