Add the fish shell to the enums and reading the config.fish only at
present.

Thought installing fish through homebrew would install under /bin/ path
but that's not the case. Add few UI changes to select and test out the
shell though not working at the moment.

Added the shell script to locate the fish config and use it. Had forgot
about it intially, on how we can locate the original fish shell config.

At this stage, we're basically running a process that calls zsh shell to
run which fish and get the path.