Add terms query doc.

docs/Query/Terms.md

+# Terms Query
+
+> More info about terms query is in the [official elasticsearch docs][1]
+
+A query that match on any of the provided terms.
+
+## Simple example
+
+```JSON
+{
+    "terms" : {
+        "tags" : [ "blue", "pill" ],
+        "minimum_should_match" : 1
+    }
+}
+```
+
+In DSL:
+
+```php
+$termsQuery = new TermsQuery(
+    'tags',
+    ['blue', 'pill'],
+    ['minimum_should_match' => 1]
+);
+
+$search = new Search();
+$search->addQuery($termsQuery);
+
+$queryArray = $search->toArray();
+```
+
+[1]: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-terms-query.html