feat(widget): add size constraint tests for TTkWidget (#630)

Co-authored-by: Copilot <copilot@github.com>

Author: ceccopierangiolieugenio

libs/pyTermTk/TermTk/TTkWidgets/checkbox.py

@@ -20,7 +20,7 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-__all__ = ['TTkCheckbox']
+__all__ = ['TTkCheckbox', 'TTkCheckBox']
 
 from typing import Optional
 
@@ -242,3 +242,5 @@ def keyEvent(self, evt:TTkKeyEvent) -> bool:
             self._pressEvent()
             return True
         return False
+
+TTkCheckBox = TTkCheckbox