Shape Shifter

Dear ImGui Licence    siv::PerlinNoise Licence

Controls:
- Hold RMB and drag to scroll the map
- Scroll to zoom in and out
- WASD to shift the heightmap around (VERY SLOW and does not work if auto regen is disabled)
Note that if a window is in focus, panning and zooming will not work. Click on the main viewport to fix this.
The "Load from string" thingy takes strings outputted by the "Copy to Clipboard" feature.