Add newline list format flag

[raiyuza]

Is your feature request related to a problem? Please describe.
I use a custom build tmux which extends tmux configuration with a subset of the tcl language.

I tried to get the project names from the list command but due an poor implementation of tcl or lack of understanding. I could only only get so so far without using quotes. The furthest i got was something like the following.

#choose from list and switch to project
bind-key P tcl {
  cd [f #{pane_current_path}]

  choose-from-list {*}[split [exec tmuxinator list | tail +2 | grep -oE {([0-9]|[aa-zz])\w+} | sort  ] "\n"] -onselect {
    exec git checkout [lindex [split [string range $_ 2 end] " "] 0]
}

All this work just to print the project names line by line, and even then i had to make additional iterations to get all the matches.

This made me wonder why can't we do something like ls -1 for the list command.

Describe the solution you'd like
I suggest creating a flag called '--newline' to print each line like such :

$> tmuxinator list --newline
barfoo
foobar
yxz

This will make it easier and i assume more compatible with other text processing commands

Describe alternatives you've considered

bind-key P tcl {
  cd [f #{pane_current_path}]

  choose-from-list {*}[split [exec sh findprojectslist.sh | sort  ] "\n"] -onselect {
    exec git checkout [lindex [split [string range $_ 2 end] " "] 0]
}

Writing my own PRQ

Additional context
This is my first issue ever created on github, any feedback is welcome!