ci: move to github actions

[alxndrsn]

Motivation

• it doesn't look like the travis integration is still functional
• brings inline with https://github.com/brianc/node-postgres/

Changes

• adds yarn.lock - this seems to be required by github actions
• drops support for node v10 - otherwise build fails with:

error postgres-array@3.0.2: The engine "node" is incompatible with this module. Expected version ">=12". Got "10.24.1"

[brianc]

this is pretty awesome!! TY!!!!