feat(tickets): added child and student ticket types

[paperclypse]

What/Why/How?

It seemed like it would be a good idea to add museum ticket types for students (reduced price) and children aged 0-5 (free) so that there are a variety of ticket prices.

(Created as part of the Write The Docs writing conference Writing Day)

Check yourself

• [ x] Code is linted
• [ ] Tested with redoc/reference-docs/workflows (internal)
• [ ] All new/updated code is covered with tests

Security

• [ ] Security impact of change has been considered
• [ ] Code follows company security practices and guidelines