Add license headers

[SimiHunjan]

Problem

Source code is missing Apache 2.0 license headers.

Solution

Add license headers

/*-
 * ‌
 * Hedera JavaScript SDK
 * ​
 * Copyright (C) 2020 - 2022 Hedera Hashgraph, LLC
 * ​
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * ‍
 */

Alternatives

No response

[easpaas]

@SimiHunjan Would you mind pasting the license headers text here for me to copy?