terminal_title parameter in config

[Canop]

Allow automating the terminal's title change.
Add this in configuration:

###############################################################
# Terminal's title
# If you want the terminal's title to be updated when you change
# directory, set a terminal_title pattern by uncommenting one of
# the examples below and tuning it to your taste.
# Note that this may slow down some systems.
#
# terminal_title: "[broot] {git-name}"
terminal_title: "🐄 {file} "
# terminal_title: "-= {file-name} =-"

Fix #794