`jwt_token` not accurately named

[aph3rson]

In the constructor for a GhApi object, the jwt_token parameter appears to be used as a bearer token, whereas the token parameter uses an Authorization: token prefix:

https://github.com/fastai/ghapi/blob/4fe9459c7e7bd631c7317eaa9d2365f14f2cb34d/ghapi/core.py#L96-L101

There are other types of bearer tokens apart from JWTs. In the app space, installation access tokens are also passed via a Bearer header, but are not JWTs. These look more like PATs, starting with ghs_.

I might recommend:

• clarifying the documentation on different ways to authenticate to the GitHub API, or pointing at the appropriate GitHub docs.
• rename the current jwt_token arg to something like bearer_token
• raise a non-fatal warning when jwt_token is specified, asking developers to use the appropriately-named bearer_token arg.