Feature request: allow multiple config files (merge)

[janderssonse]

Allow an actionlint config to build on a base config so the two are combined, instead of one fully
replacing the other. For example, you could have an Global config used in many repos, with a few overrides in special repos.

Current behavior (v1.7.12)

Exactly one config is ever loaded — first match of -config-file , then
/.github/actionlint.yaml. There's no layering: whichever is found wins outright.

Use Case

Avoid duplication among actionlint configs.
Predictable global settings

[janderssonse]

Note: would be willing to draft PR suggestion