Upgrade node-gyp devDependency from ^4.0.0 to ^5.0.0 (#119)

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "level-community": "^3.0.0",
     "level-concat-iterator": "^2.0.0",
     "mkfiletree": "^1.0.1",
-    "node-gyp": "^4.0.0",
+    "node-gyp": "^5.0.0",
     "nyc": "^14.0.0",
     "prebuildify": "^3.0.0",
     "prebuildify-ci": "^1.0.4",