chore: update repository URL (#65)

Update `repository.url` in package.json to avoid a redirect for tooling that uses it.

Author: richardlau

package.json

@@ -26,7 +26,7 @@
   },
   "repository": {
     "type": "git",
-    "url": "https://github.com/rvagg/branch-diff.git"
+    "url": "https://github.com/nodejs/branch-diff.git"
   },
   "preferGlobal": true,
   "devDependencies": {