[DOC] clarify OS Version in scanner

[sozercan]

What kind of documentation improvement is needed?

Missing information or guidance

What is the change that is needed?

Clarify this info is used to find the appropriate tooling image for the OS. This applies to deb and rpm based images today. For example, for debian, it'll discard the minor version and use the slim image with the corresponding major version (example: debian:12-slim) for Ubuntu, it'll use the major.minor. Since there's no major.minor.patch image for ubuntu, that's why it's failing in your example below. for RPM, for Azure linux, we parse X.Y.Z (for example, "2.0.20231130") but discard Z (which ends up with mcr.microsoft.com/cbl-mariner/base/core:2.0). for non-Azure Linux based RPM, just use mcr.microsoft.com/cbl-mariner/base/core:2.0 today.

Are you willing to submit PRs to contribute to documentation?

• [X] Yes, I am willing to implement it.