* 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
* MM-21368 Notify user when editing message that's too long
* Disable 'Save' button to prevent edits from being posted
* Display error message specific to the message size and allows max, instead of the current, default "Invalid Message" error.
* Split message length error into text (left justified) and counts (right justified)
UX guidance from PR review
* UX Review: Wrap for longer error text + spacing adjustment
* UX Review: Align split messages to top + add spacing in-between
* UX Review: Align error message box padding with content
