Add uptime command (#2407)

Co-authored-by: Snow <135516526+BabyBoySnow@users.noreply.github.com>

musicbot/bot.py

@@ -144,6 +144,7 @@ def __init__(
 
         self.use_certifi: bool = use_certifi
         self.exit_signal: ExitSignals = None
+        self._init_time: float = time.time()
         self._os_signal: Optional[signal.Signals] = None
         self._ping_peer_addr: str = ""
         self._ping_use_http: bool = False
@@ -6925,6 +6926,18 @@ async def cmd_checkupdates(self, channel: MessageableChannel) -> CommandResponse
             delete_after=60,
         )
 
+    async def cmd_uptime(self) -> CommandResponse:
+        """
+        Usage:
+            {command_prefix}uptime
+
+        Displays the MusicBot uptime, since last start/restart.
+        """
+        uptime = time.time() - self._init_time
+        delta = format_song_duration(uptime)
+        return Response(
+            f"MusicBot has been up for `{delta}`",
+
     @owner_only
     async def cmd_botlatency(self) -> CommandResponse:
         """