Improve Exit/Leave door icon for RoomContextualMenu

**Is your feature request related to a problem? Please describe.**
@SBiOSoftWhare It took over 2 mins to understand how to leave a room on Element-ios on my iPhone 10.

**Describe the solution you'd like**
The reason is because the leave room icon looked too much like a light/dark side split icon...instead of a door.
I think having **more** of an angle on the top and bottom of the door, along with adding a small round circle to represent a door handle would have made it much easier to understand it was in fact a Door icon and not some Split icon or Window icon.

**Describe alternatives you've considered**
do nothing; risk of continuing to confuse users.

**Additional context**
Something like:
1. https://icon-library.com/icon/icon-door-0.html
2. https://www.dreamstime.com/door-icon-flat-style-open-door-symbol-door-icon-flat-style-open-door-symbol-isolated-white-background-simple-abstract-image117467194