`provide` function unavailable in Firefox content scripts context

Our team is trying to write a browser extension to create an autocomplete search feature inside Github for a 3rd party issue tracking system.

We almost have it working on Chrome, but on Firefox the [content security limitations of content scripts](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Sharing_objects_with_page_scripts#xray_vision_in_firefox) is preventing us from making this work.

The issue is that the [`provide`](https://github.com/github/text-expander-element/blob/main/src/text-expander-element.ts#L250-L252) function sent in the detail object of the `text-expander-change` `CustomEvent` is not accessible inside the Firefox content script.

We would appreciate any refactor that would allow us to use this component without any passthrough functions or DOM fragments.

Start by reading src/text-expander-element.ts around the provide function at lines 250-252 and review how it is passed through the text-expander-change CustomEvent. Reproduce the behavior in a Firefox content script, then determine an approach that avoids passthrough functions and DOM fragments while preserving the component's autocomplete behavior.

Written by the indexing model from the issue text.