Add Mital/Bukhtawar/Ranjith to ADMINS.md (opensearch-project#15)

* Set targetCompatibility and sourceCompatibility to JavaVersion.VERSION_1_8

* Update ADMINS.md

Signed-off-by: Mital Awachat <mitalawachat@users.noreply.github.com>

Author: mitalawachat

ADMINS.md

@@ -8,6 +8,9 @@ This document explains who the admins are (see below), what they do in this repo
 | -------------------------| --------------------------------------- | ----------- |
 | Charlotte                | [CEHENKLE](https://github.com/CEHENKLE) | Amazon |
 | Henri Yandell            | [hyandell](https://github.com/hyandell) | Amazon      |
+| Mital Awachat            | [mitalawachat](https://github.com/mitalawachat) | Amazon |
+| Bukhtawar Khan           | [Bukhtawar](https://github.com/Bukhtawar) | Amazon |
+| Ranjith Ramachandra      | [rramachand21](https://github.com/rramachand21) | Amazon |
 
 
 ## Admin Responsibilities

NOTICE.txt

@@ -1,5 +1,5 @@
 OpenSearch (https://opensearch.org/)
-Copyright 2021 OpenSearch Contributors
+Copyright OpenSearch Contributors
 
 This product includes software developed by
 Elasticsearch Java Client