Try extension for each supported playbook format when no extension is specified in spec path
When the specified spec path has no file extension, the playbook builder should try the file extension for each supported format until it finds a match, or throw an error if the spec path cannot be resolved to a file.
The extensions should be tried in the following order:
- .yml
- .json
- .cson
Currently, the playbook builder only looks for file with the .yml extension, which defeats the purpose of this feature.