Updating Readme with Firewall information

[lisamurphy-msft]

Description

Updated the README.md file with Firewall information. Will keep this in Draft mode as additional requests for documentation updating might be needed here depending on the granularity we want to include.

Issue reference

The issue this PR will close: #232

Checklist

Please make sure you've completed the relevant tasks for this PR out of the following list:

• All acceptance criteria in the backlog item are met
• The documentation is updated to cover any new or changed features
• Manual tests have passed
• Relevant issues are linked to this PR

[shawngib]

Is there any value in making note that the defaults rule are specific to Azure Portal, Azure Cli and Azure PowerShell access? Meaning that is why it was done but this does cover what was done very nicely.

[lisamurphy-msft]

That is a valid point, I'm not certain what value adding context to an IT administrator is with that information.
My original thought was to be much more verbose, but it wasn't following the flow of the original documentation.