fix: invalid dir for native binaries

Author: SReject

lib/libnut-core/index.ts

@@ -24,13 +24,13 @@ export interface libnut {
 
 let libnut : libnut;
 if (process.platform === 'darwin') {
-    libnut = require("osx/libnut.node");
+    libnut = require("./osx/libnut.node");
 
 } else if (process.platform === 'linux') {
-    libnut = require("linux/libnut.node");
+    libnut = require("./linux/libnut.node");
 
 } else if (process.platform === 'win32') {
-    libnut = require("windows/libnut.node");
+    libnut = require("./windows/libnut.node");
 
 } else {
     throw new Error('unsupported platform');