Closes#2800
This PR makes it so that `check-scripts` will error out if you forget to
add a "references" entry to a tsconfig file when adding an internal
dependency in our monorepo.
If these project references are missed it can prevent TS from
building/rebuilding things when they need to be built/rebuilt.
### Change Type
- [x] `internal` — Any other changes that don't affect the published
package[^2]
It tried to get out but we're dragging it back in.
This PR brings [signia](https://github.com/tldraw/signia) back into
tldraw as @tldraw/state.
### Change Type
- [x] major
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Co-authored-by: David Sheldrick <d.j.sheldrick@gmail.com>
