Introduce build tooling

[pokey]

We'd like a way to formally indicate dependencies between artifacts / packages in our monorepo. For example,

• the website requires us to generate the root of the website as well as the docs site, and then merge them.
• we need to build the cheatsheet html bundle before we test / package Cursorless

We are leaning towards wireit, as it is quite simple / small / flexible. Another option is Turborepo, but that looks like a bigger piece of tooling

Note that Typescript's --build flag is already doing some caching / dependency management for us. We could consider letting wireit be aware of these dependencies as well. If so, we'd probably want to use our meta-updater config to automate some of these dependencies. And see https://github.com/google/wireit#recipes

Worth having a look at https://news.ycombinator.com/item?id=32600230