message: Explain `ggez` personal fork in `Cargo.toml`
  Fixes
diff: @@ -25,4 +25,6 @@ twox-hash = "1.5"
  winit = { version = "0.20.0-alpha3", optional = true }
  [dev-dependencies]
  +# A personal `ggez` fork that introduces a `FontCache` type to measure text
  +# efficiently and fixes HiDPI issues.
  ggez = { version = "0.5", git = "https://github.com/hecrj/ggez.git" }
  