Blueprint for theme starter content option

[bph]

Fixed #60

• Installs a theme with the option to install starter content, like Twenty-Twenty-One
• User lands on the homepage
• Add blueprint to gallery

[github-actions]

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Test this pull request with WordPress Playground.

[bgrgicak]

Thank you @bph!

I left one small comment related to the JSON formatting.

[bgrgicak]

Suggested change

	"options": {
	"activate": true,
	"importStarterContent": true
	}
	}
	]
	}
	"options": {
	"activate": true,
	"importStarterContent": true
	}
	}
	]
	}

[adamziel]

@bgrgicak thank you for reviewing here! Here's a cool thing – formatting issues are fine. There's an autoformatter running after merging each PR:

https://github.com/WordPress/blueprints/blob/trunk/.github/workflows/postprocess.yml