add everyting for docs

docs/snippets/get_started/quickstart/output_parser.mdx

@@ -0,0 +1,14 @@
+```python
+from langchain.schema import BaseOutputParser
+
+class CommaSeparatedListOutputParser(BaseOutputParser):
+    """Parse the output of an LLM call to a comma-separated list."""
+
+
+    def parse(self, text: str):
+        """Parse the output of an LLM call."""
+        return text.strip().split(", ")
+
+CommaSeparatedListOutputParser().parse("hi, bye")
+# >> ['hi', 'bye']
+```