docs(schema-to-ts): [PDE-5969] Minor doc updates to reference schema-to-ts package

[rnegron]

• Added schema-to-ts to workspaces key in the root package.json, so that running yarn from the root of the repo installs schema-to-ts packages as well.
  • Without this, running yarn and then yarn test would result in errors around the vitest package missing as part of the (cd schema-to-ts && yarn test) part.
• Updated some docs to mention schema-to-ts

[rnegron]

Adding schema-to-ts in the workspaces key in package.json causes the Node.js 16 testing issue mentioned here but running yarn install from the root of the repo does not install schema-to-ts's dependencies.

The ideal solution is to drop Node.js 16 and add schema-to-ts to workspaces.. I'll add a ticket for this so we don't forget. In the meantime, I've updated the CONTRIBUTING.md file.