Add example to install git in MSYS2

Author: SingingTree

README.md

@@ -72,6 +72,9 @@ Read ["Installing Rust"] from [The Book].
    $ pacman -S mingw-w64-i686-toolchain
    $ pacman -S mingw-w64-x86_64-toolchain
 
+   # Make git available in MSYS2 (if not already available on path)
+   $ pacman -S git
+
    $ pacman -S base-devel
    ```
 
@@ -98,7 +101,7 @@ Building the documentation requires building the compiler, so the above
 details will apply. Once you have the compiler built, you can
 
 ```sh
-$ make docs NO_REBUILD=1 
+$ make docs NO_REBUILD=1
 ```
 
 To make sure you don’t re-build the compiler because you made a change