# alerts: A dictionary with single-character, "alert" keys and
# corresponding "system command" values. Note that characters
# "t" (text message) and "e" (email) are already used. The
# "system command" string should be a comand with any
# applicable arguments that could be run in a terminal.
# Properties of the item triggering the alert can be included
# in the command arguments using the syntax '{property}', e.g.,
# {summary} in the command string would be replaced by the
# summary of the item. Similarly {start} by the starting time,
# {when} by the time remaining until the starting time,
# {location} by the @l entry and {description} by the @d entry.
# E.g., If the event "* sales meeting @s 2019-02-12 3p"
# triggered an alert 30 minutes before the starting time the
# string "{summary} {when}" would expand to "sales meeting in
# 30 minutes". E.g. on my macbook
#
# alerts:
# v: /usr/bin/say -v "Alex" "{summary}, {when}"
# ...
#
# would make the alert 'v' use the builtin text to speech sytem
# to speak the item's summary followed by a slight pause
# (the comma) and then the time remaining until the starting
# time, e.g., "sales meeting in 20 minutes".