feat: add log4js adapter for logging to lsp.log

[Ty3uK]

Hi!

After spending some time trying to find cause of my local problem with connection to db I found that by default sql-language-server writing log file to very specific location on macOS:

> require("os").tmpdir()
'/var/folders/t6/7glf20r966z2wq4vzvcv2hpr0000gn/T'

Btw I use neovim (meme), so first thing that I tried was calling :LspLog to check what's happened. My log was empty so I decided to check how sql-language-server do logging and finally found cause of my error.

But maybe we can fully switch from logging to temp file to logging with LSP capabilities?