feat: add shaders example to test/game

tests/game/main.lua

@@ -1,11 +1,36 @@
-function love.load()
-  Number = 0
-end
+-- Create triangle mesh
+local attributes = {
+  { "VertexPosition", "float", 2 },
+  { "VertexColor", "byte", 4 },
+}
+local vertices = {
+  { -0.5, -0.5, 1, 0, 0 },
+  { 0.5, -0.5, 0, 1, 0 },
+  { 0, 0.5, 0, 0, 1 },
+}
+local triangle = love.graphics.newMesh(attributes, vertices, "triangles", "static")
 
-function love.update()
-  Number = Number + 1
-end
+-- If you have install glsl parser with TreeSitter, the multi-line string will be
+-- highlighted like the rest of the code.
+-- See `:help love2d-glsl`
+local shader = love.graphics.newShader(
+  [[
+    varying vec4 vColor;
+    vec4 position( mat4 transform_projection, vec4 vertex_position ) {
+        vColor = VertexColor;
+        return transform_projection * vertex_position;
+    }
+  ]],
+  [[
+    varying vec4 vColor;
+    vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords) {
+        return vColor;
+    }
+  ]]
+)
 
 function love.draw()
-  love.graphics.print(tostring(Number))
+  love.graphics.setShader(shader)
+  love.graphics.draw(triangle, love.graphics.getWidth() / 2, love.graphics.getHeight() / 2, 0, 200, 200)
+  love.graphics.setShader()
 end