cmark.ex

1acb146c - Correct the flag constant for :safe

Correct the flag constant for :safe The C source (https://github.com/asaaki/cmark.ex/blob/fcd022fe9a331c182919c600af4ae1c66463f2ed/c_src/cmark.h#L520) defines CMARK_OPT_SAFE as (1 << 3) and the comment here is correct but (1 << 3) is 8 not 16.