env-ci (npm): Get environment variables exposed by CI services
Keywords: appveyor|azure-pipelines|bamboo|bitbucket|bitrise|buddy|buildkite|ci|circle|cirrus|cloudflare|codebuild|codefresh|codeship|drone|environment|git|github|gitlab|jenkins|netlify|puppet|sail|screwdriver|scrutinizer|semaphore|shippable|teamcity|travis|variable|wercker|woodpecker|circleci|cirrus-ci|continuous-integration|vsts