Move @polkadot/x-{fetch,textdecoder,textencoder,ws} (#737)

* Move @polkadot/x-{fetch,textdecoder,textencoder,ws}

* Adjust copyrights

* Fix jest aliassing

* tsconfig resolution

packages/x-textencoder/src/node.ts

@@ -0,0 +1,21 @@
+// Copyright 2017-2020 @polkadot/x-textencoder authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+import { TextEncoder as NodeTextEncoder } from 'util';
+
+export default typeof TextEncoder === 'undefined'
+  ? class {
+    #encoder: NodeTextEncoder;
+
+    constructor () {
+      this.#encoder = new NodeTextEncoder();
+    }
+
+    // For a Jest 26.0.1 environment, Buffer !== Uint8Array
+    encode (value: string): Uint8Array {
+      const encoded = this.#encoder.encode(value);
+
+      return Uint8Array.from(encoded);
+    }
+  } as unknown as typeof TextEncoder
+  : TextEncoder;