docs: Added docs about onPlayer** events

docs/defaultEvents/player/onPlayerChangeMaxMana.md

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+# `event` onPlayerChangeMaxMana
+This event is triggered when player maximum mana changes.
+
+Original: [onPlayerChangeMaxMana](https://gothicmultiplayerteam.gitlab.io/docs/0.3.0/script-reference/server-events/player/onPlayerChangeMaxMana/)
+
+## Parameters
+* `dict` **kwargs**:
+    * `int` **playerid**: the id of the player maximum mana points gets changed.
+    * `int` **oldMaxMP**: the previous maximum mana points of the player.
+    * `int` **newMaxMP**:  the new maximum mana points of the player.
+    
+## Usage
+```python
+import g2o
+        
+@g2o.event('onPlayerChangeMaxMana')
+def onChangeMaxMana(**kwargs):
+    print(f'Player {kwargs['playerid']} changed maximum mana: {kwargs['oldMaxMP']} -> {kwargs['newMaxMP']}')
+```