Provide support for generating target-specific static web pages

[edwardalee]

This PR adds commands:

npm run build:static:c
npm run build:static:p
npm run build:static:rs
npm run build:static:cpp
npm run build:static:ts

each of which will build static HTML pages that can be opened directly in a browser without the help of a server. The main page will end up in build/index.html.

[lhstrh]

The link to the multipass instructions is not dead but apparently the repo is marked private. That said, it's not being maintained, but if anyone is interested we'd be happy to transfer the repo to the lf-lang org...

[edwardalee]

It would be great to have this available, so if you can transfer the repo to lf-lang and make it public, that would be much appreciated. I will then reinstate the link.