Create tutorial on BDD

This MR adds a tutorial about creating a basic BDD test suite.

Close #10 (closed).

src/test/java/com/example/sitodo/bdd/CucumberTestSuite.java

@@ -4,14 +4,14 @@ import io.cucumber.junit.CucumberOptions;
 import net.serenitybdd.cucumber.CucumberWithSerenity;
 import org.junit.runner.RunWith;
 
+/**
+ * The test runner class that runs the executable scenarios,
+ * i.e. the feature files written in Gherkin format.
+ */
 @RunWith(CucumberWithSerenity.class)
 @CucumberOptions(
     plugin = {"pretty"},
     features = "src/test/resources/features"
 )
-/**
- * The test runner class that runs the executable scenarios,
- * i.e. the feature files written in Gherkin format.
- */
 public class CucumberTestSuite {
 }