Lower the lower dynamic buffer value to 1024

There's not a big performance difference between 8192 and 1024
so let's use less memory at the start of the connection.

doc/src/manual/cowboy_http.asciidoc

@@ -76,7 +76,7 @@ connection_type (supervisor)::
 
 Whether the connection process also acts as a supervisor.
 
-dynamic_buffer ({8192, 131072})::
+dynamic_buffer ({1024, 131072})::
 
 Cowboy will dynamically change the socket's `buffer` size
 depending on the size of the data it receives from the socket.

doc/src/manual/cowboy_http2.asciidoc

@@ -92,7 +92,7 @@ The connection window will only get updated when its size
 becomes lower than this threshold, in bytes. This is to
 avoid sending too many `WINDOW_UPDATE` frames.
 
-dynamic_buffer ({8192, 131072})::
+dynamic_buffer ({1024, 131072})::
 
 Cowboy will dynamically change the socket's `buffer` size
 depending on the size of the data it receives from the socket.

doc/src/manual/cowboy_websocket.asciidoc

@@ -249,7 +249,7 @@ options and the zlib compression options. The
 defaults optimize the compression at the expense
 of some memory and CPU.
 
-dynamic_buffer ({8192, 131072})::
+dynamic_buffer ({1024, 131072})::
 
 Cowboy will dynamically change the socket's `buffer` size
 depending on the size of the data it receives from the socket.

src/cowboy.erl

@@ -166,7 +166,7 @@ ensure_dynamic_buffer(TransOpts, #{dynamic_buffer := DynamicBuffer}) ->
 ensure_dynamic_buffer(TransOpts=#{socket_opts := SocketOpts}, _) ->
 	case proplists:get_value(buffer, SocketOpts, undefined) of
 		undefined ->
-			{TransOpts#{socket_opts => [{buffer, 8192}|SocketOpts]}, {8192, 131072}};
+			{TransOpts#{socket_opts => [{buffer, 1024}|SocketOpts]}, {1024, 131072}};
 		_ ->
 			{TransOpts, false}
 	end.