Feat/flatten array python solution

[alangnt]

Hi Codédex team,

This PR adds a working Python solution for today's Flatten Array 🪜 challenge, and updates the README.md file to add today's GitHub link.

Here's the code :

def flatten(lst):
  # first let's init a var for the flattened array
  flat_array = []

  # for each item in the list
  for i in lst:
    # if we detect another array inside of it
    # we re-apply the function recursively
    if isinstance(i, list):
      flat_array.extend(flatten(i))
    # otherwise we simply append it
    else:
      flat_array.append(i)

  # finally we return the flattened array
  return flat_array

Here's how it works :

• init a flat_array var
• for each item in the list
• we use isinstance to detect if it's an item or another array
• if an array, we recursively call the function and extend the result
• otherwise we simply append the item
• finally we return the flattened array