2021-September-04 - Prerelease - 2.6.358

Update README.md and add 'about' section (#9568)

- Add an About section
    About text is mostly inspired/pulled from the sourceforge
    README text: <https://sourceforge.net/projects/triplea/>
- Add additional map images below the new 'about' section
- Remove outdated link to wiki
- Move badges, dev badges next to dev setup and license
    next to the license section.