add py plugin references

Author: jjw24

py-plugin-examples.md

@@ -0,0 +1,8 @@
+### Plugin examples
+
+Here are some plugins which could help you build out your own or serve as a reference point:
+- IsPrime https://github.com/lvonkacsoh/Flow.Launcher.Plugin.IsPrime
+- RollDice https://github.com/lvonkacsoh/Flow.Launcher.RollDice
+- FancyEmoji https://github.com/Ma-ve/Flow.Launcher.Plugin.FancyEmoji
+- Steam Search https://github.com/Garulf/Steam-Search
+- Currency Converter https://github.com/deefrawley/Flow.Launcher.Plugin.Currency