feat(multiplayer): add rendering of other players as colored cubes

assets/shaders/player_v_shader.glsl

@@ -0,0 +1,15 @@
+#version 460
+
+layout (location = 0) in vec3 pos;
+layout (location = 1) in vec2 texCoord;
+
+uniform mat4 mv_matrix;
+uniform mat4 proj_matrix;
+
+out vec2 tc;
+
+void main() {
+    vec4 viewPos = mv_matrix * vec4(pos, 1.0);
+    tc = texCoord;
+    gl_Position = proj_matrix * viewPos;
+}