Add API exposure for platform and platform-specific protocol versions

api/src/main/java/com/velocitypowered/api/network/PlatformVersion.java

@@ -0,0 +1,12 @@
+package com.velocitypowered.api.network;
+
+import com.velocitypowered.api.network.registry.Platform;
+import java.util.List;
+
+public interface PlatformVersion {
+  Platform platform();
+
+  int protocolVersion();
+
+  List<String> supportedVersions();
+}

api/src/main/java/com/velocitypowered/api/network/registry/Platform.java

@@ -0,0 +1,10 @@
+package com.velocitypowered.api.network.registry;
+
+public interface Platform {
+  Platform JAVA = new Platform() {
+    @Override
+    public String toString() {
+      return "Java Edition";
+    }
+  };
+}

api/src/main/java/com/velocitypowered/api/network/registry/ProtocolVersionRegistry.java

@@ -0,0 +1,8 @@
+package com.velocitypowered.api.network.registry;
+
+import com.velocitypowered.api.network.PlatformVersion;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface ProtocolVersionRegistry {
+  @Nullable PlatformVersion lookup(Platform platform, int version);
+}