Add 'Github Sponsor' button for every Exchange Repo

[arm4b]

Following the changes in StackStorm Github org, we'll need to add the FUNDING.yml file for every StackStorm-Exchange repository.

See StackStorm/st2-docker#196 for the file example.

Looking closer at https://docs.github.com/en/github/creating-cloning-and-archiving-repositories/creating-a-template-repository might also help to define the directory structure for future exchange packs.

[cognifloyd]

All new repos will now have this button because the template repo (yup we have one now 😉) has this file: https://github.com/StackStorm-Exchange/ci-pack-template/blob/main/.github/FUNDING.yml

Someone needs to add this file to the rest of the pack repos, and then this can be closed.