Better build process

[tkadlec]

Right now the package is a bit heavy and pulls in a buncch of files we likely don't need. See this warning when we run vsce publish:

This extension consists of 986 files, out of which 400 are JavaScript files. For performance reasons, you should bundle your extension: https://aka.ms/vscode-bundle-extension . You should also exclude unnecessary files by adding them to your .vscodeignore: https://aka.ms/vscode-vscodeignore

We should look at pulling in a simple build process to trim this down.