[Documentation]: Add installation instructions

[bendichter]

What would you like changed or added to the documentation and why?

https://hdmf-zarr.readthedocs.io/en/latest/installation.html

The "latest" still appears as:

Do you have any interest in helping write or edit the documentation?

No.

Code of Conduct

• [X] I agree to follow this project's Code of Conduct
• [X] Have you checked the Contributing document?
• [X] Have you ensured this change was not already requested?

[oruebel]

Looks like this may be an issue with readthedocs not updating correctly. On the dev branch the docs have been updated:

https://github.com/hdmf-dev/hdmf-zarr/blob/dev/docs/source/installation.rst

[oruebel]

@mavaylon1 I believe this issue should be fixed once you make the release.