taffybar-4.0.3: doc/contrib.md

# Contributing

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If you want to help, but don't know where to get started you can check
out these issue labels:

- [Help Wanted](https://github.com/taffybar/taffybar/labels/help%20wanted)
- [Easy](https://github.com/taffybar/taffybar/labels/easy)