add logback logging and compatability. Also test Ping command.

app/src/main/java/net/tomatentum/tomatenmusic3/command/PingCommand.java

@@ -0,0 +1,27 @@
+package net.tomatentum.tomatenmusic3.command;
+
+import java.time.Duration;
+import java.time.Instant;
+
+import org.javacord.api.entity.message.MessageFlag;
+import org.javacord.api.interaction.SlashCommandInteraction;
+
+import net.tomatentum.marinara.interaction.InteractionHandler;
+import net.tomatentum.marinara.interaction.commands.annotation.SlashCommand;
+
+public class PingCommand implements InteractionHandler {
+    
+    @SlashCommand(
+        name = "ping",
+        description = "Tests bot's connection."
+    )
+    public void execPing(SlashCommandInteraction interaction) {
+        Duration ping = Duration.between(interaction.getCreationTimestamp(), Instant.now());
+        interaction.createImmediateResponder()
+            .append("Pong! " + ping.toMillis() + "ms")
+            .setFlags(MessageFlag.EPHEMERAL)
+            .respond().join();
+
+    }
+
+}