Add Runner File Commands (#684)

* Add File Runner Commands

src/Test/L0/ServiceInterfacesL0.cs

@@ -60,6 +60,7 @@ namespace GitHub.Runner.Common.Tests
             {
                 typeof(IActionCommandExtension),
                 typeof(IExecutionContext),
+                typeof(IFileCommandExtension),
                 typeof(IHandler),
                 typeof(IJobExtension),
                 typeof(IStep),