Markdown REPL sessions

[LightAndLight]

Depends on #170.

---

```ipso-repl
> 1 + 1
2
```

```ipso-repl
> if 2 == 3
. then "yes"
. else "no"
"no"
```

Write a program that can:

• [ ] Extract ipso-repl code blocks from a markdown file
• [ ] Parse and evaluate the code blocks
• [ ] If an output is present in the code block, compare it to the computed output

Hints

• pulldown-cmark is the most popular markdown parser on crates.io
• I might want to separate code block parsing into two stages: one to join the input into a single line, and one to parse the full line
  • But how would I report errors properly, then?