Documentation for Engine classes (#150)

* First documentation annotations for Popochiu class

Base description, signals, constants and public members documented.
[upd] Documentation annotations of other classes in order to make them available to access from the Popochiu docs page.

* Progress on documenting E public methods

* Finish first pass of E documentation

Comments added to all public methods and members.

* Finish documentation for PopochiuSettings

Progress on documenting PopochiuClickable.

* Finish documentation for PopochiuClickable

Restored class_name definition and extends to their previous code format because the one line approach was causing problems with showing the classes in the documentation.

* Finish documentation for PopochiuInventoryItem

Minor updates to Popochiu and PopochiuClickable docs.

* Finish documentation for PopochiuRoom

* Finish documentation for PopochiuProp, PopochiuHotspot and PopochiuWalkableArea

* Finish documentation for PopochiuRegion

[upd] Minor text order update for virtual methods.

* Progress on documenting PopochiuCharacter

* Progress in PopochiuCharacter documentation

Update a typo when refering to Popochiu.queue outside popochiu.gd documentation comments.

* Finish documentation for PopochiuCharacter

* Finish documentation of PopochiuDialog

* Finish documentation for PopochiuDialogOption.

* Finish documentation for Data classes.

PopochiuCharacterData, PopochiuInventoryItemData and PopochiuRoomData.

addons/popochiu/engine/audio_manager/audio_cue.gd

@@ -1,6 +1,10 @@
 @tool
 extends Resource
 class_name PopochiuAudioCue
+## Used to play audio files with extra properties.
+##
+## You can set the pitch (with random values), volume, and audio bus. Whether it loops or not, or
+## whether it is 2D positioned.
 
 @export var audio: AudioStream
 @export var loop := false : set = set_loop

addons/popochiu/engine/audio_manager/audio_manager.gd

@@ -1,10 +1,10 @@
-# Handles playing audio with AudioCues.
-# 
-# TODO: Create AudioHandle so each AudioCue has its own AudioStreamPlayer...
-# http://www.powerhoof.com/public/powerquestdocs/class_power_tools_1_1_quest_1_1_audio_handle.html
-extends Node
 class_name PopochiuAudioManager
+extends Node
 @warning_ignore("return_value_discarded")
+## Handles playing audio with AudioCues.
+
+# TODO: Create AudioHandle so each AudioCue has its own AudioStreamPlayer...
+# http://www.powerhoof.com/public/powerquestdocs/class_power_tools_1_1_quest_1_1_audio_handle.html
 
 const TEMP_PLAYER := "temporal"
 const AudioCue := preload('audio_cue.gd')