README: add windows installation via Chocolatey
ag can be installed as a package from Chocolatey:
@@ -101,6 +101,10 @@ or
* Win32/64
Unofficial daily builds are [available](https://github.com/k-takata/the_silver_searcher-win32).
+
+* Chocolatey
+
+ choco install ag
* MSYS2
pacman -S mingw-w64-{i686,x86_64}-ag
