Enable extensions for tail analysis diagnostic charts

[genedan]

It would be difficult for any software to anticipate all user needs out of the box, so we ought to allow extensions to make things flexible for everyone, which hopefully is something that can set this software apart from the rest. These buttons can toggle various diagnostic charts for the tail analysis:

However I just pulled whatever examples were in the chainladder documentation. Users may have different visuals in mind and these should be integrated into the app via extensions. These buttons would be a nice place for a user to say, create their own chart type and then add their own custom button via a plugin.

Inspiration for how to do this would come from the way Anki does it, via hooks:

https://addon-docs.ankiweb.net/

We'd of course have to establish our own ecosystem for sharing and installing plugins as well. But this is a good test case for a proof-of-concept.