Feat/export package version constant (#4065)

* Added auto-generated config module `env/data.js` for importing package environment vars without importing the whole `package.json`;
Refactored `http.js` to use `env/data.js` instead of package.json;

* Added `env/data.js`;
Added `env/README.md`;

* Export package version constant;

index.d.ts

@@ -162,6 +162,7 @@ export interface AxiosStatic extends AxiosInstance {
   Cancel: CancelStatic;
   CancelToken: CancelTokenStatic;
   Axios: typeof Axios;
+  readonly VERSION: string;
   isCancel(value: any): boolean;
   all<T>(values: (T | Promise<T>)[]): Promise<T[]>;
   spread<T, R>(callback: (...args: T[]) => R): (array: T[]) => R;

lib/axios.js

@@ -40,6 +40,7 @@ axios.Axios = Axios;
 axios.Cancel = require('./cancel/Cancel');
 axios.CancelToken = require('./cancel/CancelToken');
 axios.isCancel = require('./cancel/isCancel');
+axios.VERSION = require('./env/data').version;
 
 // Expose all/spread
 axios.all = function all(promises) {

test/specs/instance.spec.js

@@ -20,6 +20,7 @@ describe('instance', function () {
         'all',
         'spread',
         'isAxiosError',
+        'VERSION',
         'default'].indexOf(prop) > -1) {
         continue;
       }