Proto commits in material-foundation/flutter-packages

These 4 commits are when the Protocol Buffers files have changed:

Commit:4c2b4af
Author:Pierre-Louis Guidez

move google_fonts to packages subdirectory

The documentation is generated from this commit.

Commit:7f629e8
Author:Pierre-Louis
Committer:GitHub

Fully migrate to null-safety and upgrade all dependencies (#237) * fully migrate to null-safety and upgrade all dependencies * format * Update CHANGELOG.md

Commit:80e00d1
Author:MH Johnson
Committer:GitHub

[Google Fonts] verify file length and file hash when downloading font files. (#62) * checksum * isolate problematic test to its own file * add checksum test to generator * version bump

Commit:370d0c4
Author:MH Johnson
Committer:GitHub

[Google Fonts] Generate urls from proto fetched from fonts.google.com (#56) * Read files from protobuf * remove existing data file * add contributing.md guide * version bump