Add release notes for v0.20 - 0.25.1

[digitalcraftsman]

I tried my best insert the right meta data in the front matter.

There are some issues related to this pull requests:

• the already existing release notes were titled after the schema " release" where month is the month of the release. However, with the lately improvements of the release process we released multiple times a month. Hence I suggest to use the version number instead, e.g. "Hugo has been released"
• the title in the left sidebar (defined by title in the front matter) is sometimes a bit long and should be improved. On smaller bugfix releases I omitted the title due to the lack of content.
• The summaries of the release notes at http://localhost:1313/categories/releases/ contains Markdown that isn't rendered as such. Either we use the markdownify template func, which could mess up the layout due to headings, or we have to think about the insertion of a custom summary divider.

[digitalcraftsman]

Selected the wrong destination branch for the pr.

[rdwatters]

Not a problem. But also note that we should really be coordinating much of the issues you mentioned above with @budparr since they are likely there related. I know he had some specific ideas in mind w/r/t how the "News" section would work, etc.

[digitalcraftsman]

That are just a few things I found on the side. The pull request is actually more focused on the content itself.