As outlined in a [Swift forums post in November ’21](https://forums.swift.org/t/swiftnio-swift-version-support/53232), SwiftNIO will only support the latest non-patch Swift release and the 2 immediately prior non-patch versions.
In this commit we drop support for Swift 5.2 and 5.3.
motivation: we are not actually using symbolicate-linux-fatal in any meaningful way in CI and it's pinned to the master branch which has been removed
changes: remove symbolicate-linux-fatal fetching from Docker
motivation: cleanup docs for oss
changes:
* add useful information in readme, with pointers to examples
* update ci setup and example to use latest tools
* update contributors list
Co-authored-by: Yim Lee <yim_lee@apple.com>
motivation: enable CI
changes: add docker files support for ubuntu 16.04 and 18.04 and swift 5.0 and 5.1
note that eventyally this will need to move to AL2 docker images, but we dont have official ones yet