v1.2008071409

This release adds full draft support (save + edit), as well
as move and copy keyboard shortcuts (m & c respectively).

Changes:

• Fix variable in send handler.
• Rework the connection mock classes for better testing.
• Fix non-main window drag bar z-index.
• Fix sidebar show/hide button count.
• Tidy up the control input style.
• Make threads slide away when moving.
• Implement copy & move keyboard shortcuts.
• Yum upgrade run.
• Bump webpack dev server patch version.
• Actually fix subject header lines.
• Use switch instead of all the if statements for keyboard controls.
• Fix overflow hiding tooltip in column email threads.
• Fix z-index of header errors in non-main windows.
• Fix width of add new column form.
• Complete implementation of draft saving and editing.
• Tweak merging of single sender threads:
• Add save draft/email button to send app.
• Don't show archive button for draft threads.
• Add append email to folder API endpoint.
• Add many more Python type annotations/mypy setup.
• Move fake_imap.py -> connection_mocks.py.
• Fix header errors showing behind columns.
• Add contact icons checkbox to welcome settings flow.