Fix function type regex (#70)

Author: deanhuynh

internal/provider/function_resource.go

@@ -100,7 +100,7 @@ func (r *functionResource) Schema(_ context.Context, _ resource.SchemaRequest, r
 							Required:    true,
 							Description: "The type of this Function Setting.",
 							Validators: []validator.String{
-								stringvalidator.RegexMatches(regexp.MustCompile("^[A-Z]+$"), "'type' must be in all uppercase"),
+								stringvalidator.RegexMatches(regexp.MustCompile("^[A-Z_]+$"), "'type' must be in all uppercase"),
 							},
 						},
 						"required": schema.BoolAttribute{