Document all site configuration options with descriptions

[choldgraf]

In #1209 we discovered that there are several configuration options that are possible for the site: section, but not documented. We also discussed a broad description of the difference between site.options: and other top-level configuration keys in site. We should document all of this so that it's not lost!

Location of site frontmatter options

I believe that the possible configuration options for site: are here:

mystmd/packages/myst-frontmatter/src/site/types.ts

Lines 57 to 83 in 8e7ac4a

	export type SiteFrontmatter = {
	title?: string;
	description?: string;
	subtitle?: string;
	short_title?: string;
	thumbnail?: string | null;
	thumbnailOptimized?: string;
	banner?: string | null;
	bannerOptimized?: string;
	authors?: Contributor[];
	/**
	* Reviewers and editors are author/contributor ids.
	* If an object is provided for these fields, it will be moved to contributors
	* and replaced with id reference.
	*/
	reviewers?: string[];
	editors?: string[];
	affiliations?: Affiliation[];
	venue?: Venue;
	github?: string;
	keywords?: string[];
	funding?: Funding[];
	copyright?: string;
	contributors?: Contributor[];
	options?: Record<string, any>;
	};

and here:

https://github.com/executablebooks/mystmd/blob/main/packages/myst-config/src/site/types.ts?rgh-link-date=2024-05-15T06%3A31%3A26Z#L26-L33

Is it possible to attach description strings to each of these so that we can programmatically document them?