Option to increase thickness of Camera2D limits

[valkyrienyanko]

The camera boundary is hard to see on a project that uses 64 x 64 tilemaps. Having the option to increase the thickness of this line would make it a lot more visible. I know I can change the color from yellow to something else like black but I like having it as yellow.

[Calinou]

I know I can change the color from yellow to something else like black but I like having it as yellow.

Instead of adding a new setting (and making the already lengthy Editor Settings even longer), I think we should draw an outline instead to make the line visible on any background. This can be done by drawing a yellow line, then a black line with a slightly different offset.

This can also be done for grid lines, the X/Y axes and so on. (Less opaque lines will also use less opaque shadows.)