Add unit tests for generateNumberToBeGuessed() and isCorrectGuess() methods

- Verified structure and value bounds of generateNumberToBeGuessed()
- Tested correct and incorrect input behavior of isCorrectGuess()
- Set up JUnit 5 with @BeforeEach for Game instantiation
- Improved test readability with @DisplayName annotations

.idea/.gitignore

@@ -0,0 +1,8 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml