Update OSX build instructions

README.md

@@ -46,8 +46,8 @@ A vaguely recent version of Xcode and the corresponding command-line tools are r
 
 For personal usage, you can use pip and homebrew to install almost all of Aegisub's dependencies:
 
-    pip3 install meson
-    brew install cmake ninja pkg-config  libass boost zlib ffms2 fftw hunspell
+    pip3 install meson      # or brew install meson if you installed Python via brew
+    brew install cmake ninja pkg-config  libass boost zlib ffms2 fftw hunspell uchardet
     export LDFLAGS="-L/usr/local/opt/icu4c/lib"
     export CPPFLAGS="-I/usr/local/opt/icu4c/include"
     export PKG_CONFIG_PATH="/usr/local/opt/icu4c/lib/pkgconfig"