Ecs-logging

([69](https://github.com/elastic/ecs-logging-python/pull/69))

- Rewrite type annotations ([119](https://github.com/elastic/ecs-logging-python/pull/119))
- Don't de-dot `ecs.version` ([118](https://github.com/elastic/ecs-logging-python/pull/118))
- Make it possible override the JSON serializer in `StructlogFormatter` ([114](https://github.com/elastic/ecs-logging-python/pull/114))
- Use `fromtimestamp` instead of deprecated `utcfromtimestamp` ([105](https://github.com/elastic/ecs-logging-python/pull/105))
- Remove unused imports and fix an undefined name ([101](https://github.com/elastic/ecs-logging-python/pull/101))

- Add support for `service.environment` from APM log correlation ([96](https://github.com/elastic/ecs-logging-python/pull/96))
- Fix stack trace handling in StructLog for ECS compliance ([97](https://github.com/elastic/ecs-logging-python/pull/97))

- Allow flit-core 3+ ([94](https://github.com/elastic/ecs-logging-python/pull/94))
- Remove python2 leftovers ([94](https://github.com/elastic/ecs-logging-python/pull/94))

- Remove python 2 support ([78](https://github.com/elastic/ecs-logging-python/pull/78))
- Add global `extra` context fields to `StdLibFormatter` ([65](https://github.com/elastic/ecs-logging-python/pull/65))

- Remove python 3.5 support ([69](https://github.com/elastic/ecs-logging-python/pull/69))
- Fix an issue where APM fields would override user-provided fields even when
APM wasn't installed ([67](https://github.com/elastic/ecs-logging-python/pull/67))
- Removed `event.dataset` field handling to match