[WIP] docs: access token new endpoints(/login, /userinfo, /v2/logout)

[shawnhankim]

Background:

• Access token is added in the NGINX Plus OIDC.
• New endpoints are added in the issue of https://github.com/nginxinc/nginx-openid-connect/issues/55
  • /login endpoint
  • /userinfo endpoint
  • `/v2/logout endpoint
• Quick start guide is linked into this link to minimize the change of files. It is subject to change by creating a branch (e.g. demo) in the repo of https://github.com/nginxinc/nginx-openid-connect.
• The docs and comments of configuration for the above new features need to be enhanced for customer convenience.

Description:

• Main Docs: Edited https://github.com/nginxinc/nginx-openid-connect#readme
  • Added doctoc for automatic toc creation
  • Aroke getting started info out into new doc
• [WIP] Demo Docs: Enhanced https://github.com/nginx-openid-connect/nginx-oidc-examples/tree/main/001-oidc-local-test
• [WIP] Comments: Enhanced comments of configuration files:

  - frontend.conf
  - openid_connect_configuration.conf
  - openid_connect.server_conf
  - etc.

[shawnhankim]

@route443 :

• @jputrino is helping us edit the docs for customers' convenience as you know. Thanks @jputrino.
• This PR will only contain 1 commit, Once the PR of feature is merged into the main branch.
• In the meantime, you could find this PR if you want to only see the files changed.
• So I would appreciate it if you could review this doc as well.