[Doc] simple.hs doesn't compile (calls addWatch with FilePath instead of RawFilePath)

[dwhughes]

Haskell newbie here, please expect naivety.

Using Ubuntu 19.10 x86_64. Beware: it's unclear to me whether getHomeDirectory :: IO RawFilePath is available anywhere in the standard Ubuntu distro (despite 45 minutes' effort), so applying the "correct" fix might make this example harder to use.

I made it work by (encodeUtf8 $ pack home) but of course that's a broken approach.

% ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.6.5
% ghc simple.hs
[1 of 1] Compiling Main             ( simple.hs, simple.o )

simple.hs:13:60: error:
    • Couldn't match type ‘[Char]’
                     with ‘Data.ByteString.Internal.ByteString’
      Expected type: System.Posix.ByteString.FilePath.RawFilePath
        Actual type: FilePath
    • In the third argument of ‘addWatch’, namely ‘home’
      In a stmt of a 'do' block:
        wd <- addWatch
                inotify [Open, Close, Access, Modify, ....] home print
      In the expression:
        do inotify <- initINotify
           print inotify
           home <- getHomeDirectory
           wd <- addWatch inotify [Open, Close, ....] home print
           ....
   |
13 |     wd <- addWatch inotify [Open,Close,Access,Modify,Move] home print
   |                                                            ^^^^