enable to resize properties panel

[SharonNaemi]

Short Description

Currently, the size of the properties panel cannot be changed.

Proposed Changes

• enable to increase and reduce the size of the properties panel by adding two resize buttons

[LaviniaStiliadou]

Functionalitiy works as intended :)

However, to improve the intuitivity of the + and - button they should be somehow attached to the properties panel (maybe make them visible when hovering the property panel or in case its not visible the right side of the modeler) I'd suggest to check out the adaptability of the properties panel in the old modeler and implement it in a similar manner

I removed the resize buttons from the toolbar and added a collapse button instead (since we don't really need to make the properties panel bigger).

Update: Drag resize of properties panel

[wederbn]

When reducing the properties panel size to zero, it disappears and I`m unable to increase the size again. Maybe the collapse button can then be used to set the size to the default size of the properties panel again?