Distribute language server via npm package

[rvanasa]

This PR exposes the new TypeScript-based language server as an npm package (tentatively named mo-ide) which can be used in place of the original binary which powers the dfx _language-service subcommand.

TODO:

• Bundle the language server as a separate CLI
• Support different transport options (currently stdio, node-ipc, and socket from vscode-languageserver)
• Build standalone mo-ide binaries for GitHub releases (using pkg)
• Test the language server on Vim / Emacs
• Include patches for Vim / Emacs if necessary
• Add step-by-step instructions for configuring Vim / Emacs

Please leave a comment if you are interested in using the Motoko language server with Vim or Emacs. Thanks!

[rvanasa]

@ggreif, would you be interested in helping me test this language server on Emacs at some point (low priority)?