This commit adds a simple HashMap cache to completion requests.
On a test project the time to compute completions went from 1200ms
to 75ms and the cache contained ~300 entries when 8000 completion
items were produced by the TSC.
This is a short-lived cache and is discarded once the completion
request is finished. In a follow up commits we could make it persist
between requests.
The Deno Language Server provides a server implementation of the
Language Server Protocol
which is specifically tailored to provide a Deno view of code. It is
integrated into the command line and can be started via the lsp sub-command.
This documentation has been moved to the
Deno manual.