Add Buildkite support

[bahmutov]

Need at least setting environment variables

https://buildkite.com/docs/rest-api

[bahmutov]

Need API token with "read / write pipeline" permissions https://buildkite.com/docs/rest-api/pipelines

To get full pipeline definition

curl -H "Authorization: Bearer $TOKEN" https://api.buildkite.com/v2/organizations/cypress/pipelines/cypress-test-tiny/

Response includes

{
  "env": {
    "TERM": "xterm",
    "CYPRESS_RECORD_KEY": "2dd054e5-16af-4244-a331-5c34ca4673ec"
  }
}