Composter Indicator

Vanilla composters only show their contents from directly above. This pack adds a
readable gauge to all four sides of the block:

- **Eight fill stages** mapped to the composter's `level` property (0-8).
- **Ruler ticks** along both edges of every side, marking each fill level.
- **Active level line** drawn across the side in lime green, with the compost
  area below it tinted, so the current level is obvious from any angle.
- **Gold line at level 8** when the composter is ready to harvest.
- **Vanilla-style 16x16 pixel art** that matches the composter's dark oak look.
- **Client-side only** - no mods, OptiFine, or shaders required, and nothing is
  sent to the server.