examples.pl -- Serve example files

Locate and serve files for the Examples menu as well as examples included from overview notebooks. The examples come from two sources:

• Prolog files in the file search path examples. Such files are distributed with SWISH.
• Gitty files marked as example. Such files can be created by the users.

This module also makes the known examples available through swish_provides/1 for supporting conditional statements on example overview notebooks.

 md_eval:provides(?Term) is nondet[multifile]

Make examples available through swish_provides/1. Can be used in dynamic cells as, e.g.,:

:- if(swish_provides(example('chat80.pl',_,_))).
...
:- endif.