add user agent string (#137)

* add user agent string

* lint

Author: clickingbuttons

polygon/rest/base.py

@@ -31,7 +31,11 @@ def __init__(
         # https://urllib3.readthedocs.io/en/stable/reference/urllib3.poolmanager.html
         # https://urllib3.readthedocs.io/en/stable/reference/urllib3.connectionpool.html#urllib3.HTTPConnectionPool
         self.client = urllib3.PoolManager(
-            num_pools=num_pools, headers={"Authorization": "Bearer " + self.API_KEY}
+            num_pools=num_pools,
+            headers={
+                "Authorization": "Bearer " + self.API_KEY,
+                "User-Agent": "Python client",
+            },
         )
         self.timeout = urllib3.Timeout(connect=connect_timeout, read=read_timeout)
         self.retries = retries