Merl Sky Overlay

Adds a sky overlay with Merl's face. Requires any one of the following: - [Horizon](https://modrinth.com/mod/horizon-port) (for modern versions) - [Nuit](https://modrinth.com/mod/nuit) (for slightly older versions) - [Skyboxify](https://modrinth.com/mod/skyboxify) (for modern versions) - [Optifine](https://optifine.net/) (for old versions)