[eleventy-plugin-compress] failing with exit code 1

Just tried adding this plugin and it's failing with a `Command failed with exit code 1` every time once it hits my main index.html file

```
4:27:58 PM -> Icons: "_site/index.html" file was successfully compressed and written to disk 🙌
[11ty] Writing _site/index.html from ./src/index.md (njk)
ELIFECYCLE  Command failed with exit code 1.
```

Everything before that seems to work fine. I tried to use 11ty debug and it didn't give me any more info than that. I'm using eleventy v2.0 btw

Reproduce the failure with Eleventy v2 using the reported src/index.md to generate the main _site/index.html, starting with the plugin's compression output and the command that follows it. Done means the index file is generated and compressed without the build ending with exit code 1.

Written by the indexing model from the issue text.