refactor: add "version" prop to schematics collection schema

[davidlj95]

PR Checklist

Please check to confirm your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular-cli/blob/main/CONTRIBUTING.md#-commit-message-guidelines
• N/A Tests for the changes have been added (for bug fixes / features)
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PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

collection-schema.json file is a schema to define a schematics collection JSON file.

However, it's missing the schematics' version property used for ng update migration schematics.

Issue Number: N/A

What is the new behavior?

Add the missing version property with a description. Optional as for rest of schematics it's not used AFAIK.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[alan-agius4]

Thank you for your contribution! However, this isn’t quite right. Schematics are at a higher level and aren’t aware of ng update logic.

[davidlj95]

Thank you for your contribution! However, this isn’t quite right. Schematics are at a higher level and aren’t aware of ng update logic.

Makes sense! Thx 👍