add Lisa expert system

[vindarel]

https://github.com/youngde811/Lisa

in which section?

[Hexstream]

Expert systems are a kind of AI, surely...

[fstamour]

Yes, expert systems are AI

[figere99]

While we're at it, i'd suggest moving the following under the AI section:

• Machine Learning
• Natural Language Processing

Logic programming and theorem provers are also classic examples of symbolic ai but they fit fine under the extant section.