Add historical release notes for Qiskit API

[Eric-Arellano]

For Qiskit, it historically has a single release note file for everything: https://qiskit.org/documentation/release_notes.html. But we probably want to migrate to one file per version. It's way too big otherwise.

Where should the release note live in the UI?

Once we have a design, we need to:

1. Port the original release note file from RST to MDX. This will take forever..I'm not sure how we want to pull it off. We may want to instead not include a ton of historical release notes? Point to the RST file?
2. Figure out how Qiskit will do release notes in the future, if they keep using Reno. It's been working well for them and I suspect they'll want to keep using Reno. But how do we integrate that into MDX?

[frankharkins]

@Eric-Arellano did we make any decisions on where it'll live in the UI?

[Eric-Arellano]

did we make any decisions on where it'll live in the UI?

Yes, it will be a simple top-level folder in the left sidebar. You'll replace this here in the _toc.json (by changing the generation script):

documentation/docs/api/qiskit/_toc.json

Lines 3340 to 3344 in a36c9ba

	{
	"title": "Changelog",
	"url": "https://github.com/qiskit/qiskit/releases"
	}
	],

It should be a folder called "Release notes" and one page per minor release, e.g. "0.44".

Note that for Runtime and Provider, it instead will be a file called Release Notes, since they are so much smaller. #282