Added setAxis

[aleadbetter]

Added setAxis function from ImPlot to allow the user to select which axis they are plotting to.

[Copilot]

Pull Request Overview

This PR adds a setAxis function to allow users to select which axis they are plotting to in the ImPlot wrapper. The implementation provides a simple wrapper around ImPlot's SetAxis functionality.

• Adds C API wrapper function zguiPlot_SetAxis in the C++ layer
• Exposes the functionality through a Zig function setAxis in the plot module

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/zplot.cpp	Adds C API wrapper function for ImPlot::SetAxis
src/plot.zig	Adds Zig wrapper function and extern declaration for setAxis

[Copilot]

The setAxis function lacks documentation. Consider adding a doc comment explaining its purpose, when to use it, and how it affects subsequent plotting operations.

Suggested change

	extern fn zguiPlot_SetupAxis(axis: Axis, label: ?[*:0]const u8, flags: AxisFlags) void;
	extern fn zguiPlot_SetupAxis(axis: Axis, label: ?[*:0]const u8, flags: AxisFlags) void;
	/// Sets the current axis for subsequent plotting operations.
	///
	/// Call this function to change the active axis (e.g., x1, y2) before issuing plot commands.
	/// This affects which axis subsequent plot items will be associated with.
	/// Use this when you want to plot data to a specific axis after multiple axes have been set up.