feat(pterodactyl): updated how placeholders are parsed in get_chat_command(), updated documentation to match

.docs/pterodactyl/setup.md

@@ -127,11 +127,11 @@ achivement messages: ^\[\d{2}:\d{2}:\d{2} INFO\]: (.*) has (made the advancement
 
 The cog uses a tellraw command to send messages to Minecraft from Discord. To change this, use the `[p]pterodactyl config chat command` command.  The JSON format Minecraft uses for this is very janky sometimes, if you need help with changing the command, you can join my [Discord server](https://discord.gg/eMUMe77Yb8).
 
-Required placeholders:
+Available placeholders:
 
-- `.%U` - replaced with display name
-- `.%M` - replaced with message contents
-- `.%C` - replaced with top role color (hex)
+- `.$U` - replaced with display name
+- `.$M` - replaced with message contents
+- `.$C` - replaced with top role color (hex)
 
 Default:
 ```json

pterodactyl/pterodactyl.py

@@ -83,7 +83,13 @@ class Pterodactyl(commands.Cog):
 
     async def get_chat_command(self, username: str, message: str, color: discord.Color) -> str:
         command: str = await config.chat_command()
-        command = command.replace(".$U", username).replace(".$M", message).replace(".$C", str(color))
+        placeholders = {
+            "U": username,
+            "M": message,
+            "C": str(color)
+        }
+        for key, value in placeholders.items():
+            command = command.replace('$.' + key, value)
         return command
 
     @commands.Cog.listener()