Use following as identifier in fonts.ini for license field. License texts are
available under licenses/ directory.

Common Licenses
---------------
Apache-2.0
CC-BY-3.0
GPL-2.0
GPL-2.0+
GPL-2.0-with-font-exception
GPL-3.0
GPL-3.0+
GPL-3.0-with-font-exception
LGPL-2.0.1+
LGPL-2.1+
OFL-1.1

Other
-----
East Syriac Adiabene License
HussainiNastaleeq License
IranianSans
George-Douros

See: https://spdx.org/licenses/

TODO
----
* Cleanup: Estrangelo Edessa License
* Cleanup: SertoUrhoy License