Add learning mode

[atk]

I'm slowly working on adding a learning mode to this track. For a start, it should have

Basics (module, functions)
|
+----------------+
|                |
Booleans         Numbers            
|                |
+----------------+
|                |
Conditionals     Loops
|                |
+----------------+
|
Memory management
|
+----------------+
|                |
Strings          Arrays
|                |
+----------------+
|
Recursion

• basics: lasagna
• booleans: annalyns-infiltration
• numbers: freelancer-rates
• conditionals: leap, darts
• loops: game-of-life
• memory-management: custom-signs
• strings: poetry-club-door-policy
• arrays elysses-enchantments
• recursion: pizza-order

Comments are welcome.