Implement Devfile Selector Custom Field Extension for Backstage

[rm3l]

As a Backstage contributor contributing a template to my organization, I want users of my template to be able to pick a Devfile from a configured Devfile registry, So that I can build upon the selected Devfile to provide additional functionality. For example, my template could prompt users to select a Devfile, and then using this information, the template could include action steps to generate a starter project off of the Devfile selected.

Acceptance Criteria

• [x] It should collect input in the form of a Custom Field Extension
• [x] It should easily installable into any Backstage instance, e.g., using an NPM package
• [x] It should allow the Backstage integrator to configure the targeted Devfile registry

Related Epic: https://github.com/redhat-developer/odo/issues/7114

[rm3l]

Marking this as complete. I created a custom field extension and published it. For now, this is available as a POC under my personal GH and NPM accounts: https://github.com/rm3l/backstage-odo-devfile-plugin/blob/main/packages/devfile-field-extension/README.md

We'll create additional issues based on the next steps about this.

Remaining things to do:

• [ ] Move this away from my personal account and NPM package
• [ ] Proper tests
• [ ] Release process: automatically publish the NPM module

/close