[Improve file explorer & implement Assimp with lighting/material support]

- Reworked file explorer UI for clearer hierarchy and usability
- Actually wired up Assimp properly for model loading
- Added basic lighting support
- Added independent material support per mesh
(oh my gosh this took 4 days to actually get working, let alone not crashing 😭)

Resources/Shaders/vert.glsl

@@ -16,5 +16,6 @@ void main()
     FragPos = vec3(model * vec4(aPos, 1.0));
     Normal = mat3(transpose(inverse(model))) * aNormal;
     TexCoord = aTexCoord;
+
     gl_Position = projection * view * vec4(FragPos, 1.0);
-}
+}