Firefox overrides break native-reference-wrapper-style

It took me a while to figure out why in the [re-frame-10x](https://github.com/day8/re-frame-10x) view of my Re-frame data, from a certain point in time, the panel gets largely erased, looking as follows (the right half of the screenshot is the panel):


Having grepped through the code of that library and then of cljs-devtools, I figured out the Firefox overrides are apparently to blame -- causing this "native reference wrapper" to lose its "position: relative" style, which in turn results in its first child (effectively "position: absolute; inset: 1px", as defined by `get-inner-background-style`) to take much more space than intended. In the context of the Re-frame-10x debugging panel, it grows to fill the entire panel with its white background.

Indeed, in Chromium, the Re-frame-10x panel works fine:


I can imagine two reasonable solutions:

1. Add the "position: relative" specification (and maybe "display: inline-flex", too?) also to the native-reference-wrapper-style config in the Firefox overrides.
2. Make the CSS values specified in the overrides _extend_ the defaults instead of replacing them.

I don't know enough about why the overrides are configured as they are currently configured, so I am also not sure which would be the right way to proceed. For now, I will try to patch this bug in my user config.

Inspect the Firefox overrides and the native-reference-wrapper-style configuration, then reproduce the issue in the re-frame-10x view. Determine whether the override should preserve the native wrapper's positioning or extend the defaults; done means the panel renders correctly in Firefox without the child background filling it.

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