Add endianness file?

[beckykd]

URL to the relevant guide or resource

The file _endianness.mdx got converted from RST but never added to the TOC.

Select all that apply

• new content request
• typo
• code bug
• out-of-date content
• broken link
• other

Describe the fix or the content request.

https://github.com/Qiskit/documentation/blob/63e5fce708877bdf5d0fb8d221a53dfe50213c94/docs/build/__endianness.mdx

For new content requests - if the request is accepted, do you want to write the content?

No response

[abbycross]

We discovered that information about bit ordering does exist in our docs but it does not use the word endian anywhere, which means a search does not uncover this content. We should reconcile the old file with the new so that at the very least, a search is effective when looking for big-endian or little-endian info.