feat: create FileNode class, addChild method

packages/file-graph/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "file-graph",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "type": "module",
+  "scripts": {
+    "test": "yarn node --experimental-vm-modules $(yarn bin jest)"
+  }
+}