Add Stackblitz integration

[mirko314]

To try out the plugins and e.g edit them quickly it would make sense to add a stackblitz link for each plugin in the readme.

The markdown would have to look like e.g:

However, this link does not seem to work well in my machine, the preview gets stuck at "installing dependencies".
This needs investigation.

References: https://developer.stackblitz.com/guides/integration/open-from-github