Scenes: Conditional blocks (IF... THEN... ELSE...)

Hello everyone :slightly_smiling_face:

I’ve made fixes based on your feedback, thanks again!

A new Docker image is available:

gladysassistant/gladys:scene-if-then-else

:backhand_index_pointing_right: Tutorial: Launch a test Docker image

:warning: If you already ran the old image, remember to run:

docker pull gladysassistant/gladys:scene-if-then-else