Added call to donate after npm install (optional)

package.json

@@ -23,7 +23,8 @@
     "v:pminor": "npm version preminor",
     "v:patch": "npm version patch",
     "v:ppatch": "npm version prepatch",
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "postinstall": "opencollective-postinstall"
   },
   "repository": {
     "type": "git",
@@ -70,5 +71,13 @@
     "commitizen": {
       "path": "./node_modules/cz-conventional-changelog"
     }
+  },
+  "dependencies": {
+    "opencollective-postinstall": "^2.0.1",
+    "opencollective": "^1.0.3"
+  },
+  "collective": {
+    "type": "opencollective",
+    "url": "https://opencollective.com/live2d-widgetjs"
   }
-}
+}