added common terms docs

docs/Query/CommonTerms.md

+# Common terms query
+
+> More info about Common terms query is in the [official elasticsearch docs][1]
+
+There are so many use cases with `Common Terms` query. We highly recommend to take a look at the [official docs][1] before continuing.
+
+Lets take first example to write easy `Common query` with Elasticsearch DSL.
+
+```JSON
+{
+  "common": {
+    "name": {
+      "query": "this is bonsai cool",
+      "cutoff_frequency": 0.001,
+      "minimum_should_match": {
+          "low_freq" : 2,
+          "high_freq" : 3
+       }
+    }
+  }
+}
+```
+
+And now the query via DSL:
+
+```php
+$commonTermsQuery = new CommonTermsQuery(
+    "field_name",
+    "this is bonsai cool",
+    [
+        "cutoff_frequency" => 0.001,
+        "minimum_should_match" => [
+          "low_freq" => 2,
+          "high_freq" => 3,
+        ],
+    ]
+);
+
+$search = new Search();
+$search->addQuery($commonTermsQuery);
+
+$queryArray = $search->toArray();
+```
+
+
+[1]: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-common-terms-query.html