feat(messages): added custom media type

[sashokbg]

🤔 What's changed?

Add the ability to use custom source media type when implementing a new "flavor" for asciidoc.
Example: adding "adoc" media type.

This pull request is a requirement for the main PR: cucumber/gherkin#95

⚡️ What's your motivation?

Please read: cucumber/gherkin#95

🏷️ What kind of change is this?

• 🏦 Refactoring/debt/DX (improvement to code design, tooling, documentation etc. without changing behaviour)

♻️ Anything particular you want feedback on?

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• Users should know about my change
  • I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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This text was originally generated from a template, then edited by hand. You can modify the template here.

[aslakhellesoy]

The messages.ts file is generated from the JSON schemas in this repo. We do this for all languages to ensure compatibility.

The only way to modify messages.ts is to modify the JSON schema and run the code generation again. See CONTRIBUTING.md for details.

[sashokbg]

The messages.ts file is generated from the JSON schemas in this repo. We do this for all languages to ensure compatibility.

The only way to modify messages.ts is to modify the JSON schema and run the code generation again. See CONTRIBUTING.md for details.

Thank you for the feedback - I missed that part. Will fix when I get some free time !

[sashokbg]

Hello @aslakhellesoy I need some help - I am unable to find how to easily add a "custom" type for the MediaType without removing the validation.

This PR's idea is to enable a CustomMediaType that can be used to register anything (check cucumber/gherkin#95)

Should I add another field called "customMediaType" with type just "string" under the existing "mediaType" ?