Support 2FA authentication

[hmdfsn]

Description of issue or feature request

le-git-imate can not perform a webui commit is the user enables two-factor authentication (2FA) .
This could be addressed in accordance with #13 and #28 .

Current behavior

Once a user enables 2FA, they can not use password for the authentication and instead they must create a personal token to use as a password when authenticating to GitHub.

However, the current version of le-git-imate uses the token only to authenticate GitHub/GitLab APIs and the authentication for git-receive-pack protocol is done by password. As a result, if a user enables 2FA, they can not use the le-git-imate extension to sign the webui commits.

Expected behavior

le-git-imate must use the personal token for any authentication which means the basicAuth should be replaced with a token-based approach.