1226 Remove categories (cla: yes)

1230 [IAP] Add Java call for launchBillingFlow (cla: yes)

1231 [in_app_purchase] make payment objc (cla: yes)

1232 [IAP] Add the Dart API for launchBillingFlow (cla: yes)

1238 [Camera] remove extra space in CHANGELOG (cla: yes)

1242 Bugfix documents: webview_flutter JavascriptChannel, Example is not updated. (cla: yes)

1246 Collection literals ignores in webview flutter plugin (cla: yes)

1248 Remove left over conflict marker (cla: yes)