Improve 'insert' performance even further

[chshersh]

A few ideas after @ChrisPenner improvements:

• If the size is empty, use one
• If member is true, update the array cell and copy array

Any other ideas are appreciated 🙂

[Yu-zh]

Do you think this is beginner friendly? I would be happy to contribute.

[ChrisPenner]

@Yu-zh It may take a little learning to get used to some of the language extensions at play here; but should be pretty approachable!

The first optimization you'll probably want to use a "pattern guard" to check if the incoming map is empty, then use the one function to create a new map.

For the second optimization, you'll want to copy and slightly adapt the code in adjust here

Feel free to take a look and let us know if you have questions 😄

[Yu-zh]

@ChrisPenner Thanks! I will take a look at the code.