Lambda-notebook

New features:
- support rendering in colab
- quicker loading without the kernel (`import lamb.auto`)
- refactor metalanguage code: better support for new operators

Fixes:
- fix several polymorphic type inference issues
- improved ipython/jupyter rendering

Fix a python 3.10 compatibility bug

Fixes, improvements, changes (highlights):
- correctly pin the right traitlets version

New features:
- composition rule for index percolation in tree composition
- composition rule for vacuous nodes (with content=None)

Fixes, improvements, changes (highlights):
- improve and generalize lang.Binder behavior
- enable svgling for internal tree drawing
- improvements to the relative clause notebook

New features:
- added an explicit changelog
- experimental support for derivations shown using `svgling` trees
- full support for installation in `site-packages`, better kernel installation

Fixes, improvements, changes (highlights):
- improve derivation rendering
- improve cross-browser compatibility
- improve error messaging and handling of composition failures