Add GitHub Actions history configuration section to README.md

[matveypashkovskiy]

Only around ~5 builds/artefacts are available. Is it configurable?

[aaltat]

Actually GitHub keeps history, but defaults are small. By default the per_page is 30, which is not that much, if there plenty of matrix jobs. We should enhance our docs to point GitHub actions how more artifacts can be get.

[aaltat]

Works like a charm. When I change https://github.com/MarketSquare/robotframework-browser/pull/1447/files Then I see

and results looks better

[matveypashkovskiy]

Nice, changed the issue title