Added automation

[UlisesGascon]

Main changes

• Replace credentials.json for a environmental variable MAILGUN_API_KEY
• Added pipelines to manage changes in Mailgun
  • ci.yml to check that the changes are valid using --dry-run
  • cd.yml to apply the changes to Mailgun
• Added support for nvm and normalized node.js engine version to 18
• Docs updated

Note

I will include the MAILGUN_API_KEY secret in the repository if we agree on it, as the pipelines will require it

Changelog

• 35a3329 chore: added support for nvm by @UlisesGascon
• 0897b32 chore: normalized node.js engine version to 18 by @UlisesGascon
• 107b480 chore: replace credentials.json for a environmental variable by @UlisesGascon
• e157e40 chore: added pipelines to manage changes in Mailgun by @UlisesGascon
• 36a1c5c fix: typo by @UlisesGascon
• 90b32b6 docs: added automation step by @UlisesGascon

[mhdawson]

@nodejs/build-infra I'm asking similar questions in a few PRs related to adding tokens for access to sensitive build assets for GitHub workflows. It may just be that we should trust GitHub and we've already added equivalent tokens but I'd like to get input from other build team members on that front.