Add a "defaults" template function that returns "manifest.DefaultManifestEntry" (especially for doing "ClearDefaults" to be able to fully replicate the default output of "bashbrew cat", but in a different order)

cmd/bashbrew/cmd-cat.go

@@ -88,6 +88,9 @@ func cmdCat(c *cli.Context) error {
 			}
 			return filtered
 		},
+		"defaults": func() manifest.Manifest2822Entry {
+			return manifest.DefaultManifestEntry
+		},
 	}).Parse(format)
 	if err != nil {
 		return cli.NewMultiError(tmplMultiErr, err)