Datagrid columns are not resizable

[daltzctr]

Describe the bug
Columns are not user resizable, which is standard in a datagrid component.

Desktop (please complete the following information):

• OS: Windows 19041+
• Version: .NET MAUI 8 Preview 5

[symbiogenesis]

The columns can be resized if you bind to the Columns property and resize them via code, or set a control to be bound to the sizes in the Columns collection.

On the current master, the Sample project has a stepper control above the grid that allows resizing one of the columns.

But MAUI being cross-platform is more limited than some frameworks, and the particular design decisions of this project also limit us.

At present, I don't know of a way to implement this that would allow the user to just drag the header borders with their mouse or thumb.

But I'm very interested if anyone has any ideas.

[symbiogenesis]

Hey, look-y here. Seems promising.

Intended Use-Case:
Support things like drag, resize, etc. without having to coordinate with other gesture recognizers and/or hook into native platform pointer events / gesture recognisers.

dotnet/maui#13346