Template converter, don't skip .yaml extension.

[staffanselander]

I started running into issues when trying out the templating feature of Drone. Most of our dronefiles are using the .yaml extensions rather than the shorter .yml extension. The template converter ignores for any Dronefile that isn't using the shorter .yml extension.

This pull-request will allow the template converter to accept .yaml extensions as-well.

I believe this pull-request would also fix the issue described here: #3237

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[joshpaulchan]

This would be great, because the yaml creator UI marks the extension as .yaml - https://github.com/drone/drone-ui/blob/131c5894f2ed1419ab6616ec7c3c4e5178be1a58/src/pages/settings/templates/templates.jsx#L23