Prepare 2.9.2 release (flutter#513)

Use package_info_plus (flutter#511)

Prepare 2.9.0 release (flutter#491)

Make drawer shade and mailbox title fade to be in sync with drawer an…

…imation (flutter#310)

Update README.md (flutter#232)

Fix error in command

Update mac screenshots (flutter#165)

Former-commit-id: b0e3ae8

[Gallery] Bump version to 2.3 (flutter#321)

Former-commit-id: 7e26897

Bump version to 2.2 (flutter#247)

Former-commit-id: e1c7a14

Bump gallery to v2.1 (flutter#208)

Former-commit-id: 5971c65

Merge in the flutter gallery (flutter#176)

Former-commit-id: 563e7e6