Housekeeping - fix/upgrade all dependencies, add formatting build step.

[Bubblyworld]

Fixes #209:

• Update all dependency versions.
• Remove unused dependencies.
• Add rimraf and vscode, both are dependencies but not listed as such.
• Add prettier build step, and prettify codebase.

Not sure what to do about devDependencies, there are a lot of them that are technically dependencies because the chomp uses them, but I think it might download and cache its own binaries anyway.

[Bubblyworld]

I'm expecting tests to fail - there's a CDN builder error at the moment that's bombing one of the API tests out.

[Bubblyworld]

(but testing everything else locally works fine)

[soma-ryo]

FYI: vscode package is deprecated. Would be expected use @types/vscode and vscode-test instead. https://code.visualstudio.com/updates/v1_36#_splitting-vscode-package-into-typesvscode-and-vscodetest