Vulkan triangle!

Switched to Vulkan 1.1 GLSL dialect
Added vulkan test shader
Implemented test render thread function

standard_assets/shaders/vulkan_test.vert

@@ -0,0 +1,23 @@
+#version 450
+
+// Temporary test shader for vulkan bringup...
+// See https://vulkan-tutorial.com/Drawing_a_triangle/Graphics_pipeline_basics/Shader_modules
+
+layout(location = 0) out vec3 fragColor;
+
+vec2 positions[3] = vec2[](
+    vec2(0.0, -0.5),
+    vec2(0.5, 0.5),
+    vec2(-0.5, 0.5)
+);
+
+vec3 colors[3] = vec3[](
+    vec3(1.0, 0.0, 0.0),
+    vec3(0.0, 1.0, 0.0),
+    vec3(0.0, 0.0, 1.0)
+);
+
+void main() {
+    gl_Position = vec4(positions[gl_VertexIndex], 0.0, 1.0);
+    fragColor = colors[gl_VertexIndex];
+}