Can't publish/build on Windows (easily)

It's difficult to set this project up on Windows, and npm interactions (particularly after https://github.com/matrix-org/matrix-analytics-events/pull/31 lands for publishing) are near-impossible.

The major points of concern are:

• ../schemas/*.json doesn't expand on Windows, so the OS tries to open a literal ../schemas/*.json file (which doesn't exist). This prevents npm build from working.
• The npm scripts launch bash windows which might not expose a proper exit code when they fail, which won't necessarily fail the commands.
  • The scripts are also shell scripts, which causes issues in general for non-bash-enabled hosts.
  • A possible fix for this is to use the low-risk parts of shelljs: https://github.com/matrix-org/matrix-rust-sdk-bindings/blob/72b8b7ef7b5bef72f4d88dc45a92088b3f3a6700/crates/matrix-sdk-crypto-nodejs/check-exists.js#L7

Workaround steps for publishing (post-#31) are:

1. Use WSL
2. yarn install
3. yarn build:ts (run the prepublish script manually)
4. Go back to the host
5. Disable prepublishOnly by renaming it
6. npm publish --access public

It's obviously not great to have to jump around between VMs to do a release though.

Start with the npm scripts behind npm build and yarn build:ts, especially the prepublishOnly path, and trace how ../schemas/*.json and shell scripts are invoked on Windows. Reproduce the failure on Windows and inspect the publishing workaround. Done means build and publish commands work on Windows without manual script renaming or VM/WSL steps, with failures returning correct exit codes.