Create rtrim.md

Author: soyeric128

docs/en/sql-reference/20-sql-functions/06-string-functions/rtrim.md

@@ -0,0 +1,26 @@
+---
+title: RTRIM
+---
+import FunctionDescription from '@site/src/components/FunctionDescription';
+
+<FunctionDescription description="Introduced or updated: v1.2.659"/>
+
+Removes specific characters from the end (right side) of a string.
+
+## Syntax
+
+```sql
+RTRIM(<string>, <trim_character>)
+```
+
+## Examples
+
+```sql
+SELECT RTRIM('databendxx', 'xx');
+
+┌───────────────────────────┐
+│ rtrim('databendxx', 'xx') │
+├───────────────────────────┤
+│ databend                  │
+└───────────────────────────┘
+```