JSON schema for `view` is too restrictive

[Shati Patel]

The schema for the view property is an enum with certain "well known" views. However, the implementation allows you to use any view, including a view from a custom extension.

I suspect the enum in the schema is wrong here, since the description ("The ID (e.g. gistpad.gists) that this step is associated with.") also suggests that custom views should be permitted 🖼️

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For example, we're using this in our CodeQL code tour to focus on specific views from the CodeQL extension. This works fine, but we're getting a schema validation error 😢