Added call to donate after npm install (optional)

package.json

@@ -4,5 +4,15 @@
   "description": "Lightweight bash package manager",
   "global": true,
   "repo": "bpkg/bpkg",
-  "install": "bash setup.sh"
-}
+  "install": "bash setup.sh",
+  "dependencies": {
+    "opencollective": "^1.0.3"
+  },
+  "collective": {
+    "type": "opencollective",
+    "url": "https://opencollective.com/bpkg"
+  },
+  "scripts": {
+    "postinstall": "opencollective postinstall"
+  }
+}