Updated travis-ci config to 🤞 catch broken builds sooner

[r3h0]

The package build/test fails on linux with different errors for swift 5.2 and 5.6. I did my best to follow the travis docs, but I couldn't test that part myself. Package.resolved seems like a lite version of a lock file, so I added it following the conventions of other package managers.

[sonarqubecloud[bot]]

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