Summary:
Add two small scripts to do spell checking in .po files.
When working with Weblate, the web browser provides some spell checking with
visual hints for every translation entry.
These scripts provide spell checking for the whole file showing the faulting
words in context.
Relies on `msgexec(1)` and `aspell(1)` from `devel/gettext-tools` and
`textproc/aspell`.
It can be tested with:
`./po_spellcheck.sh ../documentation/content/es/articles/bsdl-gpl/_index.po es`
Reviewed by: carlavilla@, dbaio@
Differential Revision: https://reviews.freebsd.org/D32465
Gordon Bergling