Forge: Fix crash when CWD does not match instance directory

Forge/src/main/java/malte0811/ferritecore/mixin/platform/ConfigFileHandler.java

@@ -4,6 +4,7 @@ import com.electronwill.nightconfig.core.ConfigSpec;
 import com.electronwill.nightconfig.core.file.CommentedFileConfig;
 import malte0811.ferritecore.mixin.config.FerriteConfig.Option;
 import malte0811.ferritecore.util.Constants;
+import net.minecraftforge.fml.loading.FMLPaths;
 
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -16,7 +17,9 @@ public class ConfigFileHandler {
         for (Option o : options) {
             spec.define(o.getName(), o.getDefaultValue());
         }
-        CommentedFileConfig configData = read(Paths.get("config", Constants.MODID + "-mixin.toml"));
+        CommentedFileConfig configData = read(
+                FMLPaths.CONFIGDIR.get().resolve(Constants.MODID + "-mixin.toml")
+        );
         for (Option o : options) {
             configData.setComment(o.getName(), o.getComment());
         }