What is the change
[Describe the change here, see CONTRIBUTING.md for details]

Changes to our documentation for users, to make it easier for users to understand how to raise issues with us, and whether to raise them in llvm-project, picolibc, or here in arm-toolchain

Why this change cannot be done upstream
[Provide the rationale]

This documentation is necessarily specific to arm-toolchain. It wouldn't be welcome upstream.