The "line break" ( --- ) breaks render on second use

[jeremydouglass]

As described on this repo:

By default, only these special characters have text replacements:

• line breaks (---)

However, the "line break" (---) breaks render on second use. (It also doesn't actually render a line break, it renders a horizontal rule.)

Reproduce:

1. Go to the test interactive playground https://poems.verses.xyz/test
2. In text mode, enter the test snipper:

- a --- b --- c
- d --- e
- f

Renders:

a

---

b

Another test:

- a
- ---
- b
- ---
- c

Renders:

a

---

b

Any time that --- is used more than once it will not be rendered and no further rendering occurs.