Added Explosive Shot ability (Valkyrie)

https://app.asana.com/0/19181930247327/19174462922975
Adding two non-integrated directories for storing unfinished audio and models
Adding mission framework.

Some TODOs are missing -- mainly I'm not 100% sure how we should expand on this, I think it might be best to just add in elements as we go and make changes as needed. An example of what still needs to be added would be an element that defines what enemy type to spawn and how many of that specific type, as well as their difficulty.

https://app.asana.com/0/19050287655194/19955992770458
Merge pull request #18 from Covalent-Games/implement/missions

lgtm
Proof of concept: New targeting mechanic?

https://app.asana.com/0/19050287655194/20545417550868
FIrst iteration of targeting overhaul

So far I like this, except the right joystick needs to have smoothing added.  Using magnitude might not be the best way to detect joystick input because it causes a visually unappealing "jump" when the player starts aiming again.

https://app.asana.com/0/18992600168310/20942285089688
Attempted a few quality of life changes.

Implemented smoothing on turret rotation. Enhanced sticky targeting to not retarget if no input is detected, which prevents enemies crossing between you and your target from targeting that new enemy.

https://app.asana.com/0/18992600168310/20942285089688
Resolved comments
Merge pull request #20 from Covalent-Games/refactor/targeting

Refactor/targeting
merged
Merge pull request #17 from Covalent-Games/feature/ability/explosive_shot

Added Explosive Shot ability (Valkyrie)
Fixed minor inheritance bug preventing code compile
Merged master to feature/heatbar