[FEATURE] Skip indexing layers by digest

[sparr]

Description

A workaround for #579 is to use --min-layer-size to skip indexing a specific layer, but this may skip other layers undesirably.

Describe the solution you'd like

Add a new option to skip indexing layers based on their digest.

Describe any alternative solutions/features you've considered

No response

Any additional context or information about the feature request

No response