This PR fixes various docs issues.
* Fixes `yarn dev-docs` and `yarn build-docs` not working.
* Updated guides to get assets from the new `tldraw/tldraw` repo instead
of the old `tldraw/tldraw-examples`.
* Updated an old CodeSandbox link to the new StackBlitz. Thanks
@MitjaBezensek for spotting it!
### Change Type
- [x] `documentation` — Changes to the documentation only (will not
publish a new version)
### Release Notes
* [docs] Updated guides to get assets from the new `tldraw/tldraw` repo
instead of the old `tldraw/tldraw-examples`.
* [docs] Updated an old CodeSandbox link to the new StackBlitz.
Lu Wilson