feat: support multiple Webpack runtimes (gregberge#701)

* feat: support multiple Webpack runtimes

* namespace chunk loading global in loadableReady

* Change namespace to chunkLoadingGlobal

* Update size snapshot

Author: wvanrensselaer

.size-snapshot.json

@@ -1,13 +1,13 @@
 {
   "dist/loadable.cjs.js": {
-    "bundled": 16354,
-    "minified": 7304,
-    "gzipped": 2565
+    "bundled": 16504,
+    "minified": 7301,
+    "gzipped": 2586
   },
   "dist/loadable.esm.js": {
-    "bundled": 15975,
-    "minified": 7000,
-    "gzipped": 2495,
+    "bundled": 16125,
+    "minified": 6997,
+    "gzipped": 2516,
     "treeshaked": {
       "rollup": {
         "code": 276,

src/loadableReady.js

@@ -8,7 +8,7 @@ const BROWSER = typeof window !== 'undefined'
 
 export default function loadableReady(
   done = () => {},
-  { namespace = '' } = {},
+  { namespace = '', chunkLoadingGlobal = '__LOADABLE_LOADED_CHUNKS__' } = {},
 ) {
   if (!BROWSER) {
     warn('`loadableReady()` must be called in browser only')
@@ -49,8 +49,8 @@ export default function loadableReady(
   let resolved = false
 
   return new Promise(resolve => {
-    window.__LOADABLE_LOADED_CHUNKS__ = window.__LOADABLE_LOADED_CHUNKS__ || []
-    const loadedChunks = window.__LOADABLE_LOADED_CHUNKS__
+    window[chunkLoadingGlobal] = window[chunkLoadingGlobal] || []
+    const loadedChunks = window[chunkLoadingGlobal]
     const originalPush = loadedChunks.push.bind(loadedChunks)
 
     function checkReadyState() {