Details elements aren't searchable - a11y issue

### Have you read the Contributing Guidelines on issues?

- [X] I have read the [Contributing Guidelines on issues](https://github.com/facebook/docusaurus/blob/main/CONTRIBUTING.md#issues).

### Prerequisites

- [X] I'm using the latest version of Docusaurus.
- [X] I have tried the `npm run clear` or `yarn clear` command.
- [X] I have tried `rm -rf node_modules yarn.lock package-lock.json` and re-installing packages.
- [X] I have tried creating a repro with https://new.docusaurus.io.
- [X] I have read the console error message carefully (if applicable).

### Description

Hey folks.

The way that the details elements are implemented in docusaurus currently is incompatible with searching the page with cmd + F.

This is quite a big deal for documentation.

Closed details elements are searchable in chrome
https://chromestatus.com/feature/5032469667512320

I've tested in safari and firefox on my mac too and they also open on this page if I search for a word within
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/details

However, in my site and on the docusaurus site they aren't searchable due to the styling that animates the height change.

searching for "correlation" on this page yields no results
https://docusaurus.io/docs/markdown-features

### Reproducible demo

https://docusaurus.io/docs/markdown-features

### Steps to reproduce

searching for "correlation" on this page yields no results

### Expected behavior

the details element should open

### Actual behavior

it doesn't

### Your environment

- Public source code:
- Public site URL:
- Docusaurus version used:
- Environment name and version (e.g. Chrome 89, Node.js 16.4):
- Operating system and version (e.g. Ubuntu 20.04.2 LTS):

### Self-service

- [ ] I'd be willing to fix this bug myself.