Add terms of service

[davidfischer]

As this changes the terms of service for Read the Docs, it should not be merged without approval of either @agjohnson, @ericholscher, or both

This PR adds a terms of service for Read the Docs, Read the Docs for Business, and Documentation Sites. It updates the Privacy Policy to link to the terms.

• I wrote the terms with the intention that they apply to Read the Docs for Business
• I followed sentence case for non-H1 headings except when a term was from the definitions section
• These terms were heavily influenced (see: borrowed or lifted) from GitHub's CC-0 licensed site policies
• GitHub's terms had a whole sub-document on serving legal notice. Since we don't have that in place, I removed much of it.
• The terms are "governed by the federal laws of the United States of America and the laws of the State of Oregon"
• If you are casually reviewing this, I think a second set of eyes on the Payments/Refunds section specifically wouldn't be bad
• I tentatively put the date on the terms/privacy policy for the end of the month but this can be adjusted if and when this is merged.

Future work

• Link to this terms of service from the footer of readthedocs.org. Since our links usually link to the "stable" version of the docs, we should wait until this is released to add that link.
• Link to this ToS from the footer of readthedocs.com and replace the existing terms.
• Consider linking to this from the flyout menu on Documentation Sites

[agjohnson]

This looks great, thanks for diving into this. I added a few clarifications where the legal term was missing or unclear, but otherwise the document is thorough and I'm comfortable applying this as our terms of service.

[davidfischer]

I think all the issues are addressed if this could get another (final?) review.

[agjohnson]

Changes look good! The unresolved bit on my side was the subdomain removal note, but that looks to have been removed. That should be fine I think, we've discussed project removal already.