Add subtitles

[viriatusX]

Hi!
is it possible to update Ghosler with a checkbox to include the Subtitle?
https://forum.ghost.org/t/subtitles-in-newsletters-ghost-changelog/47949

Thanks

[ItzNotABug]

Hey @viriatusX,
Thanks for the feature suggestion.

This doesn't look too trivial to implement.
I'll bump my ghost version and take a look at how this is styled and implemented. Due to work, I cannot guarantee the ETAs on this though.

[ItzNotABug]

Completed via #59 🎉.