added raymarching demo for testing

src/shaders/shader.vert

@@ -6,11 +6,14 @@ layout(location=0) out vec2 vert_uv;
 
 layout(set=1, binding=0) uniform Uniforms 
 {
-    mat4 view_projection;
+    mat4 view; // world to camera
+    mat4 proj; // camera to screen
+    mat4 proj_inv; // screen to camera
+    vec3 cam_pos; // camera position
 };
 
 void main() 
 {
     vert_uv = in_uv;
-    gl_Position = view_projection * vec4(in_position, 1.0);
+    gl_Position = vec4(in_position, 1.0);
 }