Added common configuration file with the following exposed values: graceEnabled, graceLength and keyRefillAir. This has not been tested in LAN.

src/main/java/com/micle/loginprotection/setup/Config.java

@@ -0,0 +1,41 @@
+package com.micle.loginprotection.setup;
+
+import net.minecraftforge.common.ForgeConfigSpec;
+import net.minecraftforge.fml.ModLoadingContext;
+import net.minecraftforge.fml.config.ModConfig;
+
+public class Config {
+    public static ForgeConfigSpec COMMON_CONFIG;
+
+    public static ForgeConfigSpec.BooleanValue GRACE_ENABLED;
+    public static ForgeConfigSpec.IntValue GRACE_LENGTH;
+
+    public static ForgeConfigSpec.BooleanValue KEY_REFILL_AIR;
+
+    public static void init() {
+        initCommon();
+
+        ModLoadingContext.get().registerConfig(ModConfig.Type.COMMON, COMMON_CONFIG);
+    }
+
+    private static void initCommon() {
+        ForgeConfigSpec.Builder builder = new ForgeConfigSpec.Builder();
+
+        builder.comment("Grace period settings").push("grace");
+        GRACE_ENABLED = builder
+                .comment("Whether a player receives a grace period after becoming active or not.")
+                .define("graceEnabled", true);
+        GRACE_LENGTH = builder
+                .comment("How long the grace period lasts for a player in seconds.")
+                .defineInRange("graceLength", 10, 1, Integer.MAX_VALUE/40);
+        builder.pop();
+
+        builder.comment("Key settings").push("key");
+        KEY_REFILL_AIR = builder
+                .comment("Whether a player's air supply gets refilled upon becoming active.")
+                .define("keyRefillAir", true);
+        builder.pop();
+
+        COMMON_CONFIG = builder.build();
+    }
+}