3566 [image_picker_for_web] Add doc comments to point out that some arguments aren’t supported on the web (cla: yes, p: image_picker, platform-web)

3574 [video_player_web] Bump version for NNBD stable (cla: yes, nnbd, p: video_player, platform-web)

3584 [url_launcher] Update platforms to NNBD stable (cla: yes, nnbd, p: url_launcher, platform-linux, platform-macos, platform-web, platform-windows)

3595 [shared_preferences] Bump platform versions to NNBD stable (cla: yes, nnbd, p: shared_preferences, platform-linux, platform-macos, platform-web, platform-windows)

3622 [google_sign_in_web] Ignore analyzer checks in generated files. (cla: yes, p: google_sign_in, platform-web)