Underscores in documentation are sometimes lost

[benno5020]

Hello!

First of all, thank you for your work! Visidata is amazing and I think the website looks great too!

I've noticed the following bug:
Some underscores in the markdown docs are converted to <em> tags in the generated html.

## Grep {#grep}
A .grep file is a JSON lines file. It can be in two formats:
1) A simple container with three fields:
    file - a string with the path to the file where the match was found (absolute or relative path)
    line_no - an integer with the line number in the file where the match was found,
    text - a string with the text of the line that matched.
2) ripgrep `grep_printer` format, described here:
https://docs.rs/grep-printer/latest/grep_printer/struct.JSON.html

Source: https://github.com/saulpw/visidata/blob/ecbeaf5a50c2696060d4aafc662e877d0f976add/docs/formats.md?plain=1#L224

is converted to

<h2 id="grep">Grep</h2>
<p>A .grep file is a JSON lines file. It can be in two formats: 1) A simple container with three fields: file - a string with the path to the file where the match was found (absolute or relative path) line<em>no - an integer with the line number in the file where the match was found, text - a string with the text of the line that matched. 2) ripgrep <code>grep_printer</code> format, described here: https://docs.rs/grep-printer/latest/grep</em>printer/struct.JSON.html</p>

(Source: https://www.visidata.org/docs/formats/, note the line<em>no and https://docs.rs/grep-printer/latest/grep</em>printer)

Another occurrence can be found here: https://github.com/saulpw/visidata/blob/ecbeaf5a50c2696060d4aafc662e877d0f976add/docs/formats.md?plain=1#L80

I wanted to look into fixing it but it took me a while to find this repo and now I'm out of time - maybe you could mention it in the contribution guide? Please let me know if I can be of assistance.