Add title type

[brookewp]

After seeing the missing name field in #396, I thought it might make sense to add a 'title' type to the schema to set explicit titles. In DataViews, there are three special fields:

titleField: The id of the field representing the title of the record.
mediaField: The id of the field representing the media of the record.
descriptionField: The id of the field representing the description of the record.

When these are set, they get unique styling, which we are utilizing for image_url in the mediaField, which can be seen in the screenshots below.

This way, we don't have to guess like we do for block patterns. However, I left the check under string for sources like Airtable and Google Sheets, where we aren't explicitly defining each field and its type.

Before	After

Before	After

[github-actions]

Test this PR in WordPress Playground.

[alecgeatches]

This is great, and would definitely help with auto-generation! What do you think about string:title or something like that? Like a type with hinting instead of a separate type. We could extend the same hints for other types like id:primary, image_url:primary, string:description, etc. I like the idea of adding information to the type rather than adding a different one, but it's subjective which is preferable.