Add Bicep validation workflow

[pamelafox]

Purpose

This PR adds a GitHub workflow that checks the AZD template for best practices using Defender to DevOps. This change was part of Anthony's #325 PR but he asked me to split that up for easier review.

Does this introduce a breaking change?

[ ] Yes
[X] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[X] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

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[pamelafox]

Unfortunately, the template-analyzer can't handle the unspecified parameter that we added in order to force people to pick a good OpenAI location. I've filed microsoft/security-devops-action#65 and microsoft/security-devops-action#47

I'll close this PR for now and open a PR without the Defender validation.