Add range filter doc.

docs/Filter/Range.md

+# Range Filter
+
+> More info about range filter is in the [official elasticsearch docs][1]
+
+Filters documents with fields that have terms within a certain range.
+
+## Simple example
+
+```JSON
+{
+    "filter" : {
+        "range" : {
+            "age" : {
+                "gte": 10,
+                "lte": 20
+            }
+        }
+    }
+}
+```
+
+And now the query via DSL:
+
+```php
+$rangeFilter = new RangeFilter('age', ['gte' => 10, 'lte' => 20]);
+
+$search = new Search();
+$search->addFilter($rangeFilter);
+
+$queryArray = $search->toArray();
+```
+
+[1]: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-range-filter.html