C#: ExecuteRectClipLines (aka RectClipLines, previously) seems to be broken in 1.2.2

[AngusJohnson]

Discussed in #529

^{Originally posted by GeneralGDA May 22, 2023}
In the 1.1.1 NuGet package everything is OK. I updated to the 1.2.2 NuGet and now RectLicpLines returns the rect boundaries. For example, let's take the rect with min (0, 0), and max (8, 8). And clip with it a line: (4, 4), (4, 5), (9, 5), (9, 4), (5, 4)

I expect the output contains two separate lines. But the 1.2.2 clipper returns single line. It includes the rect boundary.

[AngusJohnson]

This is a C# only bug, and here's the fix:
Replace this line with ...
Add(ip, true);

[AngusJohnson]

Should be fixed now.