M3-2-1: Add change note for template and member exclusions

Author: lcartey

change_notes/2022-09-18-m3-2-1-templates.md

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+ - `M3-2-1` - `DeclarationsOfAnObjectShallHaveCompatibleTypes.ql`
+   - Reduced false positives by excluding non-object variables (for example, member variables).
+   - Reduced false positives by excluding variable templates and template instantiations.
+   - Improved the reported error message by including the conflicting type names.