docs: Add Fine-Tuning section for GitHub runner scaler

[silviu-dinu]

Improving GitHub scaler documentation by adding Fine-Tuning section and highlighting current limitations.

Checklist

• Commits are signed with Developer Certificate of Origin (DCO)

Fixes #6519

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[zroubalik]

This is great, one minor nit, from this version is it not clear what limit has the current implementation (vs the older one has 30).

Could you please update this?

[silviu-dinu]

This is great, one minor nit, from this version is it not clear what limit has the current implementation (vs the older one has 30).

Could you please update this?

@zroubalik Thanks! That's a good point. It's changed now.

[zroubalik]

Thanks!