Add toggle buttons to hide the Chat/Teams sidebar and also expand the message pane
Add buttons next to the top-left Teams icon to toggle the sidebar and also to expand the message pane.
Tested in Chrome and Firefox with Tampermonkey and Violentmonkey.
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1.2.0 - Detect theme changes and update icon colors
1.1.0 - Add function to expand message pane
1.0.0 - Initial release
