* Added monster drops

Monsters can now be configured to drop items based on a resource (MonsterDrops.gd).
The usability is not the greatest, but that's due to not being able to export custom types. 
There were two possible approaches that I saw:
1. An `Array` holding dictionaries for each item that can be dropped along with the data needed for the drop behavior.
2.  Create a custom resource that would encapsulate all the data for the items that can be dropped from a monster: The item itself, min and max quantities, and the chance. 

I decided to go with the first one.

ps: The items are _NOT_ being added to the player's inventory . This is just the functionality needed for the monsters to start dropping items.

Closes #59

* Embedded drops array to battler template, fixed code issues

Use class_name for pawns and derivatives
Make it so followers are not registered in the grid so they don't collide with the player's pawn
Rename classes to Pawn* to make it clear they're related to the map/grid

Added CoC based on GNU Kind Communications Guidelines

* Refactor Actor and standardize naming convention

* Add Leader and Follower

* Remove unnecessary look direction signal

* Fix moved signal emission passing the same position

* Move pawns to a YSort container

Concept arts integrated into the combat system

Had to remove the typed part of the `execute()` function from CombatAction.gd. It wasn't a `void` anymore: it returns if it actually managed to hit a target. When changing the function type to bool, yields would throw an error. I'm not sure if this is a bug with typed GDScript.

The only "missing" point is converting the game from 720p to 1080p. For
what I can tell, it's already 1080p, but it's being tested as 720p.

I had to downscale the sprites for the battlers, they were occuping the
whole screen.

For the platforms, I decided to only hide the sprite:
- The platforms might be used in a different area theme in the future
- The characters already have their own shadow
- Shadows have different sizes depending on what battler is "casting" it

Closes #53

To have add/remove functions as part of the api
Changed some names for more common English words

Add basic item and inventory handling
closes #44
closes #45 
closes #47 

Implement minimal Attack and UseSkill CombatAction

Added CHANGELOG.md by following git commits.

Reduces a lot of the object designs to be reusable resources that act as templates for factory methods.

* Update the readme, write about characters and a little bit about combat

Part 2 of #13

* first mockup for grid movement

* back to defaul enviroment

* Get the right information when creating the battle scene from the localmap scene

* first mockup for grid movement

* back to defaul enviroment

* Get the right information when creating the battle scene from the localmap scene

* substitute Game scene with the one with local map

* add local map and transition from it to combat

* cleanup incongruences between versions

* Add localmap to the scene

* bugfix for wrong indentation in Battler.gd . Avoid continously transition to combat if the player keeps the direction button towards the enemy (in the map)

* Deleted template comments; Class, script and filename renamed in CamelCase;
Signal in LocalMap connected in parent node.

Mana bars added

The bars system has been refactored. It's now possible to easily extend
it to create different bars i.e. stamina, rage, energy, etc..
The interface anchor has been removed and replaced with a proper control
node to hold the bars. Folder structure has also been cleaned.

Note that the newly added manabar will not show as of now since the
characters do not have mana at level 1 (not sure why). They were
configured to only appear if the battler has more than 0 of max mana.

Closes #31

Add Character Growth

Characters gain experience points at the end of battle, which contribute to their level.  Levels determine stat growth along defined curves for each character.

Skills system added

It's now possible to add skills as resources and use them in combat.
Some changes:

- Initial stats now have mana
- A combat action for skills has been added
- A really simple menu to select which action to perform in the given
turn
- Resource for skills
- Skills can be executed on a given chance

What can be improved:
- As of now, the skills have a `base_damage` which is added on top of the
already calculated damage in the `Hit` script. We might want to use the
strength as a multiplier to increase the overall damage of the skill,
for instance, instead of just adding them together.

- The menu for selecting the action is really simple and the UX is bad
to say the least. I'll create a separate issue for this.

- Skills are only available as a form of attack, i.e. you can't create
healing skill with the current system. But it can be extended to do so.

- They are not specific to jobs. For instance, both Dan and Blue are
fighters, but you'll have to add skills to them separately. Though, this
is most due to how they were created. We should probably create a
separate FighterJob and add the skills to them, this would fix the
problem imo.

Closes #16 and #15

Part 2 of #13

Prototype monster AI, choose target based on health