you can add that to the skin you use.
find this part in the variables.yaml from the skin you use:
#
# Custom head includes - should be a YAML List, e.g.:
#
#head_includes:
# - some include
# - some other include
#
# Text will be included verbatim in the head section of the doc, use for styles,
# javascript or 3rd party css etc. etc.
#
# It is your responsibility to ensure the HTML is correct
#
#head_includes:
# -
#