Add debug console functionality to Janet LSP

[CFiggers]

Learn from the excellent design of Textual's devtools: https://textual.textualize.io/guide/devtools/

Essentially, on startup have Janet LSP check for the presence of a debug console on a standard (or command-line argument parameterized?) port. If one is found, connect and route debug messages to it.

[CFiggers]

Minimal implementation delivered with #15 . Some additional polish might be good—in particular, considering using alternate screen buffer with \e[?1049h and restoring on server exit.