More Jupyterlite docs/functionality

[chrispyles]

Updates docs to include details about running on Jupyterlite and Colab, as well as some updates to using Otter Assign with Jupyterlite assignments

Closes #458

[chrispyles]

Leaving this PR in draft state until I add a better workflow for testing assignments locally (since the test url prefix won't work yet) and update assign to automatically default to test files when a url prefix is provided (instead of metadata tests).

[codecov]

Codecov Report

Merging #496 (12903fb) into beta (d243498) will decrease coverage by 0.16%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             beta     #496      +/-   ##
==========================================
- Coverage   65.68%   65.52%   -0.17%     
==========================================
  Files          91       91              
  Lines        5380     5384       +4     
==========================================
- Hits         3534     3528       -6     
- Misses       1846     1856      +10     

Impacted Files	Coverage Δ
otter/assign/__init__.py	75.92% <ø> (ø)
otter/assign/assignment.py	94.54% <ø> (ø)
otter/assign/cell_generators.py	92.98% <100.00%> (+0.25%)	⬆️
otter/assign/notebook_transformer.py	88.80% <100.00%> (ø)
otter/assign/output.py	83.33% <100.00%> (+0.37%)	⬆️
otter/test_files/metadata_test.py	56.25% <0.00%> (-18.75%)	⬇️
otter/test_files/__init__.py	53.19% <0.00%> (-2.84%)	⬇️
otter/check/utils.py	67.27% <0.00%> (-1.82%)	⬇️
otter/assign/tests.py	79.83% <0.00%> (+1.61%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d243498...12903fb. Read the comment docs.