Include changes from skalyan91

Manually apply changes from these two commits (I left out accent changes
on k and h):
https://github.com/skalyan91/EB-Garamond/commit/27884d499391d7cb4556aaebb2bd731bcb075e17
https://github.com/skalyan91/EB-Garamond/commit/f93f206202940ec6d6e59781ada001049debe3bc
add a context testfile