Fix typos discovered by codespell

Author: cclauss

CHANGELOG.rst

@@ -143,7 +143,7 @@ Release History
     if isinstance(event, Ping):
         bytes_to_send = connection.send(event.response())
 - Separate the handshake from the active connection handling. This
-  allows the handshake and connection to be seperately used. By
+  allows the handshake and connection to be separately used. By
   default though WSConnection does both.
 - ``receive_bytes`` is renamed to ``receive_data`` and
   ``WSConnection`` should be imported from ``wsproto`` rather than
@@ -155,7 +155,7 @@ Release History
 - Support h11 ~0.8.1.
 - Support Python 3.7.
 - Make the close-handshake more explicit, by sending a close frame on
-  reciept of a close frame.
+  receipt of a close frame.
 - Bugfix fix deflate after a non-compressable message.
 - Bugfix connection header acceptance, by accepting Connection header
   values that are comma separated lists.

docs/source/advanced-usage.rst

@@ -56,7 +56,7 @@ A WebSocket connection starts with a handshake, which is an agreement
 to use the WebSocket protocol, and on which sub-protocol and
 extensions to use. It can be advantageous to perform this handshake
 outside of `wsproto`, for example in a dual stack setup whereby the
-HTTP handling is completed seperately. In this case the
+HTTP handling is completed separately. In this case the
 :class:`Connection <wsproto.connection.Connection>` class can be used
 directly.