feat(proxy): proxy for aiohttp,base sessions (#284)

* feat(proxy): proxy for aiohttp,base sessions

Add support for proxies in aiohttp session with aiohttp_socks library,
edit BaseSession class to support proxies for other sessions in future.

* fix(annotation): missing underscore before "private" typevar

* chore: remove redundant of proxy_url schema for socks version

* test: add missing test

Add missing test, remove BaseSession.cfg and switch to
implementing class' "private" traits, add aiohttp_socks in dependency list as
optional and extra.

* feat(session):

Implement asyncio session for requests [wip]

* feat(proxy chain): Chained proxy support in aiohttp session

Add ChainProxyConnector support, !pin pydantic to "1.4", add
documentation on aiohttp connector.

* style(mypy): apply linter changes

* tests(mock): remove await for magic mock

* fix dangling dependency

* refactor(generic):

get rid of generic behaviour for base session

mkdocs.yml

@@ -41,6 +41,9 @@ nav:
   - install.md
   - Bot API:
       - api/index.md
+      - Client:
+            - Session:
+                  - aiohttp: api/client/session/aiohttp.md
       - Methods:
           - Available methods: api/methods/index.md
           - Getting updates: