Miscellaneous updates based on feedback

[cormacpayne]

This PR resolves the following items:

• https://github.com/Azure/container-apps-deploy-action/issues/17
  • Introduces the location argument to specify the region that the Container App will be deployed to
  • Added documentation for this argument to call out how to find valid locations
• https://github.com/Azure/container-apps-deploy-pipelines-task/issues/4
  • Introduces the environmentVariables argument to specify a list of environment variables to set on the deployed Container App
  • Originally introduced by @Basssiiie in PR https://github.com/microsoft/azure-pipelines-tasks/pull/17595
• https://github.com/Azure/container-apps-deploy-pipelines-task/issues/6
  • Handles the OS of the agent that is executing the Azure DevOps Task to account for commands are executed and how the pack CLI is installed
  • Originally introduced by @icornett in PR https://github.com/Azure/container-apps-deploy-pipelines-task/pull/5
• https://github.com/Azure/container-apps-deploy-pipelines-task/issues/3
  • Improves documentation to call out how the pack CLI is being installed by the task
• Improves validation for provided arguments
• Improves argument documentation and examples