Declare types for node builtins modules within REPL virtual file

[cspotcode]

Node lets you do util.promisify() within the REPL without importing util because it declares getters for each builtin module.

However, ts-node doesn't tell typescript about these getters, so you'll still get TS errors if you try to util.promisify

We can add a bunch of declare const to the top of the REPL file so that all built-ins are declared.

Limitations:

• Should gracefully skip when @types/node is not available