feat: wait on multiple urls

[bahmutov]

• closes support multiple wait-on values #152
• closes Run cypress tests in github actions, running up front-end and back-end http servers. #128

Separate urls with a comma

with:
  working-directory: examples/wait-on
  start: npm start -- --port 3050, npm run start2 -- --port 3060, node ./index3 --port 3070
  # wait for all services to respond
  wait-on: 'http://localhost:3050, http://localhost:3060, http://localhost:3070'

[github-actions]

🎉 This PR is included in version 2.5.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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