Add TerminalConsoleAppender for console prompts

proxy/src/main/java/com/velocitypowered/proxy/Velocity.java

@@ -1,12 +1,13 @@
 package com.velocitypowered.proxy;
 
+import com.velocitypowered.proxy.console.VelocityConsole;
+
 public class Velocity {
-    public static void main(String... args) throws InterruptedException {
+    public static void main(String... args) {
         final VelocityServer server = VelocityServer.getServer();
         server.start();
 
         Runtime.getRuntime().addShutdownHook(new Thread(server::shutdown, "Shutdown thread"));
-
-        Thread.currentThread().join();
+        new VelocityConsole(server).start();
     }
 }

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -56,8 +56,7 @@ public class VelocityServer implements ProxyServer {
     private final CommandInvoker consoleCommandInvoker = new CommandInvoker() {
         @Override
         public void sendMessage(@Nonnull Component component) {
-            // TODO: TerminalConsoleAppender
-            logger.info(ComponentSerializers.PLAIN.serialize(component));
+            logger.info(ComponentSerializers.LEGACY.serialize(component));
         }
 
         @Override

proxy/src/main/java/com/velocitypowered/proxy/console/VelocityConsole.java

@@ -0,0 +1,39 @@
+package com.velocitypowered.proxy.console;
+
+import com.velocitypowered.proxy.VelocityServer;
+import net.minecrell.terminalconsole.SimpleTerminalConsole;
+import org.jline.reader.LineReader;
+import org.jline.reader.LineReaderBuilder;
+
+public final class VelocityConsole extends SimpleTerminalConsole {
+
+    private final VelocityServer server;
+
+    public VelocityConsole(VelocityServer server) {
+        this.server = server;
+    }
+
+    @Override
+    protected LineReader buildReader(LineReaderBuilder builder) {
+        return super.buildReader(builder
+            .appName("Velocity")
+            // TODO: Command completion
+        );
+    }
+
+    @Override
+    protected boolean isRunning() {
+        return !this.server.isShutdown();
+    }
+
+    @Override
+    protected void runCommand(String command) {
+        this.server.getCommandManager().execute(this.server.getConsoleCommandInvoker(), command);
+    }
+
+    @Override
+    protected void shutdown() {
+        this.server.shutdown();
+    }
+
+}