[lint] Fix import order

Reorder imports to be consistenly grouped by standard library, third
party library, and local modules in that order thoughout the library.

discord/webhook.py

@@ -24,12 +24,13 @@ FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
 """
 
-import aiohttp
 import asyncio
 import json
 import time
 import re
 
+import aiohttp
+
 from . import utils
 from .errors import InvalidArgument, HTTPException, Forbidden, NotFound
 from .user import BaseUser, User