added conf file to build readthedocs page

[alek-p]

i've already configured http://openzfs.readthedocs.io/ to build from this repo.
I think adding this file is the last step needed to publish this docs repo at http://openzfs.readthedocs.io/

[gmelikov]

@alek-p could you describe your plan first, please? This PR surprised me, I wonder what problems we try to solve and how we add any redirects from old links if we change them in the first place.

• https://openzfs.github.io is already well-indexed by google and others, and it's usually first in search results
• we should have only one place with same docs, and maybe other places - have redirects to first one

[gmelikov]

My first thought is - add redirect from readthedocs to https://openzfs.github.io and call it a day, in this case we won't have additional service in dependencies (rtd), save all already working links and minimize the work. But it'd be great to look at other thoughts you originally had before that.

[alek-p]

I don't see an issue with having both the GitHub.io page and the readthedocs one live at the same time and having the same info. This is what this PR would do and is the goal for me.

This is something that came up at the dev summit. The immediate problem we were trying to solve is to remove the old out of date docs from https://openzfs.readthedocs.io site and replace them with the ones we maintain as well as gaining control of the readthedocs page. There is too much old and or outdated info about zfs out there on the web and the readthedocs site has some authority in the open source community.

If we think we should only have one place for docs we could address that later on but I don't see the need to do that now.

[gmelikov]

I don't see an issue with having both the GitHub.io page and the readthedocs one live at the same time and having the same info. This is what this PR would do and is the goal for me.

It's harmful for indexing of our documentation in search engines (my past SEO experience screams, sorry), I've prepared redirection code here #585

If you don't mind redirects from RTD to https://openzfs.github.io/ - it should work. Otherwise - we can change main domain in future, but it's better to have one main domain at a time.

PS: mirror pages on rtd may have problems with /openzfs-docs/ prefix, jfyi, it may even give some problems with my redirection code, but I can easily fix it if there's a mechanism to deliver code there.

[gmelikov]

I'll merge both this PR and #585 to unblock you, but for future reference - there's additional parts to build man pages and feature matrix, which don't needed if we just want to redirect to https://openzfs.github.io/