4069 [image_picker] remove unused imports from example (cla: yes, waiting for tree to go green, p: image_picker)

4071 [in_app_purchase_android] fix version for ‘add payment proxy’: pull/4055 (cla: yes, p: in_app_purchase, platform-android)

4072 [image_picker_platform_interface] Migrate image_picker to package:cross_file (cla: yes, p: image_picker)

4073 [image_picker] Migrate image_picker to package:cross_file (cla: yes, waiting for tree to go green, p: image_picker)

4074 Add a link to the new wiki page about plugin and package PRs (cla: yes)

4075 Add link to the version update entry (cla: yes, waiting for tree to go green)