Added enhanced toFormData implementation with additional options support; (#4704)

Updated default notation for arrays and objects to bracket style;
Added `multer/express.js` tests;
Updated README.md;

Co-authored-by: Jay <jasonsaayman@gmail.com>

package.json

@@ -40,6 +40,7 @@
     "coveralls": "^3.1.1",
     "dtslint": "^4.2.1",
     "es6-promise": "^4.2.8",
+    "express": "^4.18.1",
     "formidable": "^2.0.1",
     "grunt": "^1.4.1",
     "grunt-banner": "^0.6.0",
@@ -66,6 +67,7 @@
     "load-grunt-tasks": "^5.1.0",
     "minimist": "^1.2.6",
     "mocha": "^8.2.1",
+    "multer": "^1.4.4",
     "rollup": "^2.67.0",
     "rollup-plugin-terser": "^7.0.2",
     "sinon": "^4.5.0",