Add parameter hints

[wade-cheng]

Problem

I believe parameter hints are generally a helpful feature of LSPs.

Consider the Python code

import random
random.randint(1, # <cursor location>

Ah shoot, does randint include the upper bound or not?

So, parameter hints let the user read the documentation (and confirm the order of parameters) without needing to jump to the function definition, hover over the function with a mouse, or otherwise disturb the flow of coding.

They can be toggled off for those who don't enjoy using them. Thus, this should be a strictly positive addition to Millet.

Solution

I (and probably others) would greatly appreciate an implementation of parameter hints for Millet.

(P.S. Thanks for the wonderful LSP! It's really nice to use already :) )