Workflow capabilities are available to test through a trial account.
This tutorial provides instructions on how to start working with workflows, starting with setting up an Okta account, although it is not specific to workflow connectors.
There is an Okta Workflow community you may be interested in joining, including office hours and a Slack community. Please check out the resources section at the end of the tutorial.
The link you referenced in your original post is related to Workflows, where Okta is able to make requests to third party services based on Connectors that were built especially for Workflows. These connectors still require that the admin that configures the workflow to authenticate the connector themselves.
From your use case, I don’t actually see how Okta factors into this beyond there being an Okta Application that users access. Sounds to me like your integration would need to be directly integrated to connect to Github.