Implemented fire method

[Iranon]

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I created a generic ammo folder, with an ammo script inside, and a missile folder with a missile scene and a custom sprite. The smoke effect can be removed for performance issues because it is very small into the level scene.
Missile (or bullet) should rotate with te towers.
I hope everithing is fine.

[davcri]

Thanks for opening the issue pull request @Iranon! I'm going to review it in the next days! Hopefully tomorrow :)

[davcri]

👍

[davcri]

Hi @Iranon thanks for the PR, I just merged into master! Finally we have missiles 🚀

I made some changes that you can find here:

• 0de0e40
• 54c49ec

Feel free to ask if you have any doubt about it. I thought it was easier to actually show the changes than to write a review.