feat: migrate to ESM modules & fix master tagging

[hertzg]

Should fix #47 #41 as well

[github-actions]

Builds

[
  "alpine-3.15.0-21.05",
  "debian-buster-21.05",
  "alpine-3.15.0-20.11",
  "alpine-3.14.3-20.11",
  "alpine-3.13.7-20.11",
  "alpine-3.12.9-20.11",
  "debian-buster-20.11",
  "alpine-3.15.0-20.02",
  "alpine-3.14.3-20.02",
  "alpine-3.13.7-20.02",
  "alpine-3.12.9-20.02",
  "debian-buster-20.02",
  "alpine-3.15.0-19.08",
  "alpine-3.14.3-19.08",
  "alpine-3.13.7-19.08",
  "alpine-3.12.9-19.08",
  "debian-buster-19.08",
  "alpine-3.15.0-18.12",
  "alpine-3.14.3-18.12",
  "alpine-3.13.7-18.12",
  "alpine-3.12.9-18.12",
  "debian-buster-18.12",
  "alpine-3.15.0-18.05",
  "alpine-3.14.3-18.05",
  "alpine-3.13.7-18.05",
  "alpine-3.12.9-18.05",
  "debian-buster-18.05",
  "alpine-3.15.0-0.1",
  "alpine-3.14.3-0.1",
  "alpine-3.13.7-0.1",
  "alpine-3.12.9-0.1",
  "debian-buster-0.1",
  "alpine-3.15.0-0.01",
  "alpine-3.14.3-0.01",
  "alpine-3.13.7-0.01",
  "alpine-3.12.9-0.01",
  "debian-buster-0.01",
  "alpine-3.15.0-master",
  "alpine-3.14.3-master",
  "alpine-3.13.7-master",
  "alpine-3.12.9-master",
  "debian-buster-master"
]