world-wide-what exercises: add titles in the readme

subjects/action-reaction/README.md

@@ -1,3 +1,5 @@
+## Action - reaction!
+
 ### Instructions
 
 OK, you have now connected HTML, CSS and JS altogether ; big day! Excited? Exhausted?

subjects/baby-shower/README.md

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-### Baby shower
+## Baby shower
+
+### Instructions
 
 It's time to celebrate the arrival of your creation in this world ; let's organize a baby shower!
 

subjects/bring-it-to-life/README.md

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+## Bring it to life
+
 ### Instructions
 
 Still there? Well done! But hold on, here begins the serious part... In order to control your creation, you're going to plug its brain: JavaScript.

subjects/class-that/README.md

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+## Class that!
+
 ### Instructions
 
 Alright, your being is almost done, some elements still need a bit more shaping and then we'll make it come to life!

subjects/first-words/README.md

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+## First words
+
 ### Instructions
 
 Now that you know how to make your creation move, what about making it communicate its first words to the world?

subjects/nesting-organs/README.md

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+## Nesting organs
+
 ### Instructions
 
 Bravo! You displayed the global shape of your entity, but now it's time to populate each division ; let's add up some organs!

subjects/select-and-style/README.md

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+## Select & style
+
 ### Instructions
 
 Now that you created & identified properly the different sections of your being,

subjects/skeleton/README.md

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+## Skeleton
+
 ### Welcome
 
 Welcome to the `world-wide-what` quest!

subjects/the-calling/README.md

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+## The calling
+
 ### Instructions
 
 Congrats! You created the very first base for your being and you witnessed its