http: header: add default User-Agent header

As customary with API libraries, it is useful for server operators to
know which library makes requests to it. This sets the default to the
library + version.

Signed-off-by: Frank Villaro-Dixon <frank@villaro-dixon.eu>

Author: Frankkkkk

overpy/__init__.py

@@ -75,7 +75,9 @@ class Overpass:
     #: Default URL of the Overpass server
     default_url: ClassVar[str] = "http://overpass-api.de/api/interpreter"
 
-    default_headers: ClassVar[Dict[str, str]] = {}
+    default_headers: ClassVar[Dict[str, str]] = {
+        'User-Agent': 'python-overpy/{} (urllib)'.format(__version__),
+    }
 
     def __init__(
             self,