Add user-definable description property to collection

[AndrewSisley]

Add user-definable description property to the (local) collection (client.CollectionDescription, GQL SDL, JsonPatch), and display the description via the GQL type system.

GQL Descriptions in an SDL is defined in the spec: https://spec.graphql.org/October2021/#sec-Descriptions

Note: graphql-go does not support parsing of comments/descriptions from the SDL: graphql-go/graphql#116

Adding them via PatchCollection should be pretty trivial, we can always do that first, then figure out the SDL problem later. We could as a temporary workaround have a @description directive.

Related to #1385