Add FontStruction “Insular Typewriter”

A monospaced insular font that simulates a hypothetical typewriter from the British Isles. Equipped with diacritics to write all Celtic languages, including Irish, Scottish Gaelic, Welsh, Cornish and Breton. There is also an experimental take on the Greek and Cyrillic alphabets for adding a bit of Insular flavour to other languages.

* FontStruct: https://fontstruct.com/fontstructions/show/1006913/insular_typewriter
* Github: https://github.com/FontStruct/google-fonts-contributions/tree/master/fontstructions/1006913
* Designer: https://fontstruct.com/fontstructors/25776/cmunk