Add Pepperminty Wiki (#556)

* Add Pepperminty Wiki

* Change license code to match everything else.

* Fix license, MPL2 -> MPLv2

Ref https://github.com/Kickball/awesome-selfhosted/pull/556

README.md

@@ -888,6 +888,7 @@ See also [Documentation Generators](#documentation-generators), [Wikimatrix](htt
   * [Mediawiki](https://www.mediawiki.org/wiki/MediaWiki) `PHP`
   * [MoinMoin](https://moinmo.in/) - An advanced, easy to use and extensible WikiEngine with a large community of users.
   * [Olelo](https://github.com/minad/olelo) - Olelo is a wiki that stores pages in a Git repository, supports many markup styles and has an extensible, hackable architecture. ([Demo](http://gitwiki.org/)) `MIT` `Ruby`
+  * [Pepperminty Wiki](https://github.com/sbrl/Pepperminty-Wiki/) - A complete markdown-powered wiki contained in a single PHP file. ([Demo](https://starbeamrainbowlabs.com/labs/peppermint/build/) - Read only) `MPLv2` `PHP`
   * [PmWiki](http://www.pmwiki.org) - Wiki-based system for collaborative creation and maintenance of websites.
   * [Raneto](http://raneto.com/) - Raneto is an open source Knowledgebase platform that uses static Markdown files to power your Knowledgebase - `MIT` `NodeJS`
   * [Realms](https://github.com/scragg0x/realms-wiki) - A git-backed wiki inspired by Gollum. `Python`