Create config and infrastructure for a What's new in docs for a release

[BillWagner]

I think there are a number of tasks to use the what's new tool to generate a New docs for .NET 7 page:

• [X] Add a new config file
• [ ] Add the ".NET 7 Release" label to all pertinent PRs.
• [ ] Create TOC and Index locations to put the new release-based article
• [ ] Update the title and filename for the new release-based article
• [ ] Update config section to create a release-based section for what's new.
• [ ] Create a shell script (or an action) to create a release based article when requested.

[BillWagner]

I can test the project locally running the following command from the root of my local copy.

dotnet whatsnew --owner dotnet --repo docs --savedir .\docs\whats-new --startdate 11/01/2021 --enddate 11/09/2022 --localconfig .\.whatsnew.release.json

[gewarren]

@BillWagner How can I help with this? Do you want me to add the labels to the PRs?