Managing redirects on RTD

## Status Quo
Currently, we are managing redirects by manually editing Nginx configuration files. It's not the worst thing, but it's tedious. Most of the pains are coming from that it's managed separately.

## Proposal
Read the Docs provides the [user-defined page redirects feature](https://rtd-with-docsearch.readthedocs.io/en/latest/user-defined-redirects.html#id2). It would be nice if this can be used, at least for in-project redirects, when moving pages around.

## Implementations
- https://pypi.org/project/readthedocs-cli/
- https://github.com/nextstrain/readthedocs-cli
- https://github.com/honzajavorek/rtd-redirects

## See also
- https://docs.readthedocs.com/dev/stable/design/redirects.html

Start with the linked Read the Docs redirects documentation and design proposal, then compare the listed readthedocs-cli implementations. Identify how this repository currently manages Nginx redirects and determine how in-project redirects could be managed through Read the Docs. Done means the redirect workflow is integrated without manual Nginx edits.

Written by the indexing model from the issue text.