Migrate from CircleCI to Github Actions

[tishun]

Change motivated by @dmaier-redislabs

We'd like to migrate the CI/CD from CircleCI to the Github Actions.
Actions taken:

• remove al mentions in the code base of the CircleCI, including any existing configurations
• retrofit an YAML configuration from the CircleCI to a Github Actions one
• update README.md

[dmaier-redislabs]

Looks good to me