Yaml file extension for Holopin bot on GitHub does not work

[marcduiker]

A contributor used this filename holopin.yaml instead of holopin.yml and this resulted in the Holopin bot not working and mentioning a configuration issue:

Seems like there's something wrong with your config. See [this page](https://docs.holopin.io/integrations/github#beta) for more information.

See dapr/website#93.

Expected behavior
The holopin bot should be able to work with both yaml and yml files, since both are valid. The yaml docs even mention that yaml should be preferred.