Add inline documentation to all tags, global objects and filters

[charlespwd]

As a first step, we started completing tags, variables and filters.

To make the dev experience even better, we should also send documentation and detail properties as per the Language Server Protocol spec:

	/**
	 * A human-readable string with additional information
	 * about this item, like type or symbol information.
	 */
	detail?: string;

	/**
	 * A human-readable string that represents a doc-comment.
	 */
	documentation?: string | MarkupContent;

https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_completion

[charlespwd]

Scored 13 because we need custom docs/summaries for all the tags, filters and objects in the repo. Might be able to grab stuff from the shopify.dev.

[charlespwd]

We did this a while back