Allow V3 API to be forced with an access token in use

[charles-dyfis-net]

Since #102, the V4 (graphql) API has been used whenever access tokens are provided.

However, the graphql API does not support fine-grained personal access tokens; attempting to use them results in an error (Personal access tokens with fine grained access do not support the GraphQL API). For users wishing to use such tokens, the V3 API appears to be the only available option.

CC: @kirillbilchenko

[taylorsilva]

Fine-grained personal access tokens are now supported by the GraphQL API: https://docs.github.com/en/graphql/guides/forming-calls-with-graphql#authenticating-with-graphql