Develop a version for Toolkit for YNAB

[polltery]

https://github.com/toolkit-for-ynab/toolkit-for-ynab hosts a number of plugins for YNAB. A version for their toolkit would be nice, although it will have to be done in a different repository. A link here to the repo and PR can be maintained here.

Their feature documentation to get started: https://github.com/toolkit-for-ynab/toolkit-for-ynab/blob/main/docs/building-features.md

Making use of their observe(changedNodes: Set): void should be good enough for this. I recommend this to be done after fixing #3, which can used for shouldInvoke() method.