Add examples of links to part of our lessons

**Work in progress. Don't merge it.**

Add examples of links to glossary entry and challenge.

## TODO

- [ ] Made changes based on comments
- [ ] Add changes to HTML files
- [ ] Squash changes to HTML into previous commits
I don't want people to have to include links like this explicitly - I was hoping that if we only used **bold** for new keywords, we could auto-generate the links for them.