stbi: add resize image function

[Casper64]

Add the stbi_image_resize.h thirdparty file so it's possible to resize images that are loaded with stbi.load(path).

This pr adds the ability to resize images with stbi.stbi_resize_image.

Usage

module main

import os
import stbi

fn main() {
vroot := @VEXEROOT
	path := os.join_path(vroot, 'examples', 'assets', 'logo.png')
d_s := stbi.load(path) or { panic(err) }

new_width, new_height := 100, 100
d_r := stbi.stbi_resize_image(d_s, new_width, new_height) or { panic(err) }

out_path := 'test.png'
stbi.stbi_write_png(out_path, d_r.width, d_r.height, 4, d_r.data, d_r.width * 4) or {
		panic(err)
	}
}

🤖 Generated by Copilot at 8ce0922

This pull request adds image resizing functionality to the stbi module, using the third-party library stb_image_resize. It also adds a test function to verify the resizing works as expected.

🤖 Generated by Copilot at 8ce0922

• Define macro and include header for stb_image_resize library (link,link)
• Add wrapper function for resizing images using stb_image_resize (link)
• Add test function for resizing images and checking dimensions and channels (link)

[spytheman]

#include "stb_image_resize.h" should be added in stbi.c.v around line 34 as well

[Casper64]

#include "stb_image_resize.h" should be added in stbi.c.v around line 34 as well

Just found it myself. Added it.

[spytheman]

The stbi_ prefix for the name of the V wrapper here, is superfluous.

In the caller, that role is served by the module name, i.e. C.stbi_load is wrapped by load, and in the call sites, it is stbi.load, similarly, C.stbi_resize_uint8 can be wrapped by resize_uint8, and be available as stbi.resize_uint8 in the call sites.