Add shaded outline to procedural tool textures

[yel0h]

This adds a shaded outline consistent with the item's existing lighting model, using 2 new colors per material, one for the side facing the light, one for the side away from it.

Material gains outlineColorLight and outlineColorShadow fields. They can be set via new optional outlineColorLight and outlineColorShadow hex keys in a material's .zig.zon data, and otherwise default to darkened versions of the material's existing colors palette extremes. TextureGenerator.generate now paints background pixels that border an occupied cell with the neighboring material's outline color, picking light vs shadow based on the same heightmap-derived light value already used for interior shading (this was factored out into a new calculateLight helper). The colorInt to Color conversion was also factored into colorFromInt and reused.

Closes #1062

[SpellDigger]

not to be that guy but some picture examples when holding the tool would also be useful instead of just inventory screenshot

[ikabod-kee]

I like this.
I do have one criticism though:
I think that the outline should go inside of the texture rather than outside.
As this PR makes the tools look much too thick.

[careeoki]

I like this. I do have one criticism though: I think that the outline should go inside of the texture rather than outside. As this PR makes the tools look much too thick.

Yes, but that wouldn't work with some of our tool textures, some areas are only 2 pixels wide, so the whole thing would be outlines. I think it would be best to just manually update the tool textures (i will do this)

[careeoki]

An oversight: Outline pixels are not taken into account to determine if pixels are connected or not (if a tool is not fully connected it will have 0 durability)

Despite being visually connected by the outlines, the game considers it unconnected.

[careeoki]

There are certain situations where I would like to have "corner pixels" rather than just a pixel on each side. For the ends of handles or the tip of the pickaxe head, and such.

I don't really know how you would approach this though.

[yel0h]

Okay, so connectivity check fixed, and I've managed to find a way to do the corners procedurally.

Basically, for every single-pixel tip it finds the angle of the segment ending in that tip, and then paints the diagonal pixel which best matches that angle.

[careeoki]

Basically, for every single-pixel tip it finds the angle of the segment ending in that tip, and then paints the diagonal pixel which best matches that angle.

Awesome! That seems to work well.

Though there's something I didn't consider with using the outlines to define connections. In this situation, none of the interior pixels are actually connected, but the outlines are touching so it is considered connected. Maybe instead, we allow the interior pixels to check for diagonal neighbors?
That would allow the handle here to be connected, but the disconnected parts of the pick head would not be.

Also, I opened a PR on your branch with my pickaxe texture so you can test with it. I'll be working on the other tools as well.

[careeoki]

I made another PR for the rest of the tools.

The only other thing I encountered is that our swords are no longer pointy:

Again, I don't have any ideas.

Otherwise, this seems to be good, I could move this into code review once you merge my PR.