Documenting how to modify individual policies

- Documenting individual policy change process
- Aligning documentation for multiple email addresses
- Fixing typos on:
  - _index.md
  - Customize-Policy-Assignment.md
  - Introduction-to-deploying-the-ALZ-pattern.md
- Fixing ALZMonitorResourceGroupTags value in the parameter file
- Removing the customization of ALZMonitorResourceGroupTags