Changelog visibility and formatting

[jagerber48]

This issue raises 2 issues.

1. Right now the changelog is only visible in the source code. We should make the changelog viewable in the online documentation. This is especially important for the 4.0.0 release which will make breaking changes.
2. The first changelog version started a convention of indenting lines after the first line in any changelog entry by one space. This causes a behavior that I consider to be bad where the text from the first line is bolded but text from subsequent lines is not. We should change the entries so that each line has the same indentation.

[wshanks]

Including the changelog in the documentation and fixing the formatting sound good to me. I recommend separating out the user facing changes from the developer changes so that the changelog is more readable for a user (because a user cares about things like deprecation warnings or behavioral changes but not changes to the CI or testing).