Update fix_inversion.json for immutables.github.io (#223)
Update fix_inversion.json for immutables.github.io (#223)

https://immutables.github.io/ and https://immutables.github.io/immutable.html are some documentation pages I reference a lot.

In dark mode, all the code samples become white. This fixes that.

Original CSS style being overridden:
```css
.illustration, .documentation .highlight {
...
    background-color: #2B303B;
...
}
```
darkreader/darkreader,darkreader/darkreader,alexanderby/darkreader,alexanderby/darkreader,alexanderby/darkreader,darkreader/darkreader