Plugin: auto-generate sample operation from docs

Figuring out the structure of a query, but especially a mutation is a little tricky when you are new to an API but this is probably exactly what a lot of developers will be doing most of the time.

How about a button in the Documentation Explorer [SAMPLE] that generates a sample mutation from the schema and loads it into the query window. I can then modify the values that it suggests to something valid and try the mutation to see if it works.