mermaid plugin

[bjsi]

• I updated to the latest plugin API version
• I made some small changes:
  • Register powerup before using the powerup filter in registerWidget (otherwise you get an error on the first run)
  • Update manifest to give ReadCreateModify permissions
  • Removed text changed event listeners - they aren't needed because the RemChanged event will fire if the mermaid Rem's text changed.

Please check everything is still working for you :) This is can be merged and upload to the marketplace when you are ready!

[karthikcodes6]

@bjsi all looks good. I just updated the README for this plugin.