Adding GitHub organization scanning

[samsmithnz]

Dropping the -r argument will scan the owner/organization. Partly addresses #41.

• First get a list of all repos
• Iterate through each repo, scanning it
• How can we handle rate limit exhaustion? Perhaps look at the rate limit and calculate if there is enough calls left to complete the transaction?
• How can we handle massive organizations? Can we scan an org and if it's more than n abort?
• Can we add parallel processing. If we get multiple pages of data, can we process each page in parallel?

[samsmithnz]

This is become complicated - and I'm not sure this is worth it - there are too many situations where an organization has too many repos and this will exhaust rate limits. Officially pausing this feature.

[samsmithnz]

.NET 5 bug is fixed in #52

[samsmithnz]

Closing, this was addressed with #132