Schematic brush update

What's Changed

• We've got a new schematic brush! This brush will replace the original stencil brush!
  See the documentation: https://github.com/KevinDaGame/VoxelSniper-Reimagined/wiki/brushes#schematic-brush

Forge

• Implemented the signbrush
• Forge is now feature complete!
• Fix drain brush

For the technical snipers

• Implemented ForgeSign, added tab-completion to SignOverwriteBrush by @Lennart99 in #197
• Implemented final Forge features by @Lennart99 in #199
• Feat/stencil by @KevinDaGame in #201
• 8.12 by @KevinDaGame in #206

Full Changelog: v8.11.2...v8.12.0