Test the build output

[johannes-lindgren]

We should add a test that tests that the build works as expected; for example, that the exports in package.json is configured correctly.

1. Include a new workspace package that imports immer-yjs as "immer-yjs": "file:../pure-parse",
2. In CI/CD Build the library, then run the unit tests for this package.

If immer-yjs is configured incorrectly, the tests fails.