Doc changes inspired by Google indexing feedback

[grumpyinca]

Google sent an email message with alerts to various issues that were apparently discovered by their web crawling / indexing activities. Much of this was broken links (404 errors) that are apparently left over from changes made last summer where the CNAME was incorporated, and content moved from SpringDesignSoftware.org to Heroku. It is not clear why Google is still attempting to index these now nonexistent links.

See: #685, #840

In the process of investigating, Nu HTML Checker was used to scan for related issues. Links tested included:
https://odop.springdesignsoftware.org/docs/
https://odop.springdesignsoftware.org/
https://www.springdesignsoftware.org/

As a result, one planned change is:
RegEx
from: \[(.*)\]\((.*)About\)
to: [$1]($2About/index.html)

This issue provides a branch to support this set of related changes.

[grumpyinca]

From Pat:
This message – "Duplicate without user-selected canonical" – is different from the 404s:

Google has indexed the version of https://odop.springdesignsoftware.org/ without the backslash (/) at the end, so the version with the backslash listed here (https://odop.springdesignsoftware.org/) is not indexed. You can add a canonical tag saying which version of a URL should be the one Google should reference to get rid of this message, but again, I do not think it is materially impacting your site and is more of a heads-up. I've seen similar messages with other clients.