Add fox cow to cowsay
    
    The fox cow is included in the Debian/Ubuntu package of cowsay.
    
    Author has released it under the same license as cowsay itself:
    https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=888229
    
    Tested:
    
    ```
    $ cowsay -f fox 'Crazy like a fox!'
     ___________________
    < Crazy like a fox! >
     -------------------
             \     ,-.      .-,
              \    |-.\ __ /.-|
               \   \  `    `  /
                    /_     _ \
                  <  _`q  p _  >
                  <.._=/  \=_. >
                     {`\()/`}`\
                     {      }  \
                     |{    }    \
                     \ '--'   .- \
                     |-      /    \
                     | | | | |     ;
                     | | |.;.,..__ |
                   .-"";`         `|
                  /    |           /
                  `-../____,..---'`
    ```