dependencies haskell-mode and hindent should be listed in Package-Requires of shm.el

[jian-lin]

shm-case-split.el requires1 haskell-process which is part of haskell-mode. shm-reformat.el requires2 hindent. These dependencies should be listed in the Package-Requires of main file shm.el.

ref: NixOS/nixpkgs#335442