Add Compatibility matrix

Added table that shows compatible and tested products.

Signed-off-by: Vijayan Balasubramanian <balasvij@amazon.com>

Author: VijayanB

COMPATIBILITY.md

@@ -0,0 +1,27 @@
+## Compatibility
+
+### Matrix for Logstash OSS
+
+|  logstash-output-opensearch | Logstash OSS|
+| ------------- | ------------- |
+| 1.0.0+  | 7.13.2  |
+
+### Matrix for OpenSearch
+
+|  logstash-output-opensearch | OpenSearch  |
+| ------------- | ------------- |
+| 1.0.0+  | 1.0.0  |  
+
+
+### Matrix for ODFE
+
+|  logstash-output-opensearch |  ODFE |
+| ------------- | ------------- |
+| 1.0.0+   |   1.x - 1.13.2 |
+
+
+### Matrix for Elasticsearch OSS
+
+|  logstash-output-opensearch |  Elasticsearch OSS|
+| ------------- | ------------- |
+| 1.0.0+   |  7.x - 7.10.2      |