v0.13.90

Changes

Updates go version in workflows (#1835)
Adds a link to semver documentation to clarify that version is not a prefix regexp.
The value ^1.15 is a so called "caret" range
that matches 1.15 and any minor version above, e.g. 1.16 which could be
seen in the action logs:

Setup go stable version spec ^1.15
Found in cache @ /opt/hostedtoolcache/go/1.16.7/x64
Added go to the path
Successfully setup go version ^1.15
go version go1.16.7 linux/amd64

Docker image

Docker image is available in Zalando's Open Source registry:

docker run -it registry.opensource.zalan.do/teapot/skipper:v0.13.90 skipper --help
# arm64
docker run -it registry.opensource.zalan.do/teapot/skipper-arm64:v0.13.90 skipper --help
# arm v7 32bit
docker run -it registry.opensource.zalan.do/teapot/skipper-armv7:v0.13.90 skipper --help