Create new character uren

[Nico-Sanchez]

Motivation

Uren!
Closes #983

Summary of changes

• Make projectiles able to spawn pools when they explode
• Add Uren character and skills params in seeds
• Add uren to playable characters list
• Update arena version

How to test it?

Play with front-end's branch https://github.com/lambdaclass/champions_of_mirra/pull/2229
And in browser localhost:3000/
Everything should work as usual, including Uren!

Checklist

• Tested the changes locally.
• Reviewed the changes on GitHub, line by line.
• This change requires new documentation.
  • Documentation has been added/updated.

[tvillegas98]

Seems great! some things that I would change as a balance change

1. Maybe the ultimate has too much range, it is very hard to land
2. Increase a bit the damage of the basic

Also, let's create the script for importing uren