Refactored module exports; (#5162)

* Refactored build pipeline;
Added module exports tests;
Added missing ESM export for parity with Axios factory;
Added `toFormData`, `formToJSON`, `isAxiosError`, `spread`, `isCancel`, `all` as named export to `index.d.ts`;

* Added ESM entry test;

* Updated README.md `installing` section;

* Added TypeScript importing test;
Added missed `CanceledError` & `AxiosHeaders` to `AxiosStatic` interface;

* Exclude `/test/module/` from tslint;

tslint.json

@@ -1,6 +1,11 @@
-{ 
+{
   "extends": "dtslint/dtslint.json",
   "rules": {
     "no-unnecessary-generics": false
+  },
+  "linterOptions": {
+    "exclude": [
+      "test/module/**"
+    ]
   }
 }