Increase minimum pywebview on Windows to fix PyInstaller issue

Fixes #134

requirements.txt

@@ -8,9 +8,9 @@ timeago  # for displaying the last authenticated activity hint
 # force pystray version with dummy GUI fix for headless deployments (https://github.com/moses-palmer/pystray/issues/118)
 pystray>=0.19.4
 
-# force pywebview 3.5+ on Windows to fix authentication window crash bug (https://github.com/r0x0r/pywebview/issues/720)
+# force pywebview 4.0.2+ on Windows to fix PyInstaller/pythonw issue (https://github.com/r0x0r/pywebview/issues/1044)
 pywebview; sys_platform != 'win32'  # (specify platform to avoid double requirement error with older pip versions)
-pywebview>=3.5; sys_platform == 'win32'
+pywebview>=4.0.2; sys_platform == 'win32'
 
 # macOS: improve menu bar interaction, provide native notifications and handle system events
 pyobjc-framework-Cocoa; sys_platform == 'darwin'