* Refactor post draft component
Re-styled ReadOnly channels
Remove filename from upload error
* Update canSubmit based on file attachment changes
* Fix error message for max file size
* Fix select autocomplete values on iOS
* Style readonly and refactor accessory view for iOS
* Make PostDraft scrollViewNativeID prop not required
* Update ReadOnly to have a background with 0.40 opacity
* Update max file size error message
* Fix shift+enter with HW keyboard
