Remove browser.ts global reference (#856)

* Remove browser.ts global reference

* fallback text

* formatting

* Additional formatting

* global > self > window > this

* Add x-global package

* Update tests

* Correct jest mapping

packages/x-textdecoder/src/browser.ts

@@ -1,8 +1,10 @@
 // Copyright 2017-2021 @polkadot/x-textencoder authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
+import { xglobal } from '@polkadot/x-global';
+
 import { TextDecoder as Fallback } from './fallback';
 
-export const TextDecoder = typeof global.TextDecoder === 'undefined'
-  ? Fallback as unknown as typeof global.TextDecoder
-  : global.TextDecoder;
+export const TextDecoder = typeof xglobal.TextDecoder === 'undefined'
+  ? Fallback as unknown as typeof xglobal.TextDecoder
+  : xglobal.TextDecoder;