Improve documentation of advanced ADO-specific functionality

## Description

I don't so much know if this is a bug, as it is a lack of documentation. Trying to utilize the `ado2gh generate-script` command with `--rewire--pipelines` requires a service connection to the GitHub app "azure pipelines" to exist. What isn't documented is that the connection name in ADO needs to be the GitHub organization name you are going to be migrating into. I couldn't find that documented anywhere and only realized it looking at the file [AdoApi.cs](./src/Octoshift/AdoApi.cs) line 183.

But that brings me to a larger problem of documentation around the `ad2gh` offering in general. It's pretty scarce (or possibly just spread-out?) and customers who are trying to use this could really use a little more direct assistance.

## Reproduction Steps
1. Create a GitHub PAT
2. Install the "Azure Pipelines" app to your organization in GitHub
3. Create an ADO PAT
4. Create the "Service Connection" in ADO (name it "github")
5. Attempt to run `ado2gh generate-script` with your parameters including `--rewire-pipelines`
6. The script will say:
> CANNOT FIND GITHUB APP SERVICE CONNECTION IN ADO ORGANIZATION...

7. Rename the "Service Connection" in ADO to be the same as the organization in GitHub
8. Attempt to run the script again. This time it will succeed.