3260 [cross_file] An abstraction to allow working with files across multiple platforms. (cla: yes)

3261 [file_selector] Allow empty type groups (cla: yes)

3263 [google_maps_flutter_platform_interface] Add a fromJson constructor. (cla: yes)

3269 [device_info_platform_interface] Remove default types and correct nullable types (cla: yes)

3271 [wifi_info_flutter] Edit sample wifi_info_flutter plugin (cla: yes)

3273 [google_maps_flutter_web] Render custom Marker icons. (cla: yes)

3276 Fix outdated links across a number of markdown files (cla: yes, waiting for tree to go green)

3279 Use testWidgets instead of test to fix failures not surfacing on CI (cla: yes)