Basic APIs

Thank you for your amazing work! I hope another feature request won't put too much effort on you.. anyway, hope this will be helpful.

I think it will be helpful if some basic APIs can be released, for the users to write userscripts easier for themselves. Eg

1. the document that is being read
2. run time
3. the location of the cursor is in zathura
4. export bookmarks/quickmarks explicitly
5. the last selected section

..etc