This is to better integrate with more advanced shell history managers
like McFly and Atuin. By initializing fzf first, we allow the history
managers to steal the C-r key binding from fzf.
The environment variable FZF_CTRL_R_COMMAND has never existed
and been support by fzf according to
`git grep FZF_CTRL_R_COMMAND $(git rev-list --all)` and
`git log -G FZF_CTRL_R_COMMAND`.
This allows you to specify your own custom commands
to be run when calling fzf. You might use tools like
fd to search faster and take `.gitignore` files into
consideration.
