Describe the bug
When using the kernel.CreatePluginFromPromptDirectoryYaml(...) method, if the files you are trying to load are using the .yml extension instead of .yaml, the files are not loaded.

To Reproduce

1. Create a valid YAML prompt template with a .yml extension in a folder
2. Try to create a plugin for that folder
3. Notice that the plugin is loaded without any functions

Expected behavior
Ideally, the method would support both file extensions since it is common for them to be used interchangeably. If supporting the .yml extension is out of the question, this behavior should be documented.

Screenshots
If applicable, add screenshots to help explain your problem.

Platform

• Language: C#
• Source: https://github.com/microsoft/semantic-kernel/blob/3b53b7fb10d25fff78bc5d6183cd17550054b2f1/dotnet/src/Functions/Functions.Yaml/PromptYamlKernelExtensions.cs#L89C1-L89C49
• AI model: N/A
• IDE: N/A
• OS: N/A

Additional context
I haven't confirmed, but this behavior may exist in the non-C# versions of the SDK as well.