Add CHANGELOG + Small nits for #552

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Add ability to declare an included Taskfile as optional
+  ([#519](https://github.com/go-task/task/issues/519), [#552](https://github.com/go-task/task/pull/552)).
 - Add support for including Taskfiles in the home directory by using `~`
   ([#539](https://github.com/go-task/task/issues/539), [#557](https://github.com/go-task/task/pull/557)).
 

docs/usage.md

@@ -166,6 +166,7 @@ includes:
   tests:
     taskfile: ./tests/Taskfile.yml
     optional: true
+
 tasks:
   greet:
     cmds:

taskfile/read/taskfile.go

@@ -60,10 +60,10 @@ func Taskfile(dir string, entrypoint string) (*taskfile.Taskfile, error) {
 		}
 
 		info, err := os.Stat(path)
-		if err != nil && includedTask.Optional {
-			return nil
-		}
 		if err != nil {
+			if includedTask.Optional {
+				return nil
+			}
 			return err
 		}
 		if info.IsDir() {