* Extend the cspell word list
* Remove those extensions from individual source files
* white-list licenses and such as we should not meddle with those
* Fix spelling
Move "internal" crates into the `internal` directory. This first batch
includes most of sixtyfps_runtime but leaves the rendering backends
alone for now.
pre-commit applied some cleanups to the moved files:
- Consistent newline at end of file policy
- trimming trailing whitespace
- Formatting Cargo.toml files.