Provide LLM With Language Server Types

[mathewpareles]

When we send messages to an LLM, we want to provide context about relevant types the user can access (including variable and function types). For example, if the user imports the React package, we should give the LLM context about the various attributes in the React object, like React.useContext, React.useState, etc.

We're open to any solutions that inject useful type information into LLM prompts. This will involve accessing vscode's internal language server, and modifying the sendLLMMessage function to include types in the context.