use github actions to build docker images

[sidey79]

Build process via github actions

• Added a workflow which builds the fhem docker image for serveral architectures via buildx supported plattforms
• Upload for test of the images currently provided to github container registry if there is a secret token provided,

disabled travis CI builds

• Due to missing travis credits, the travis yaml file is renamed to not force any more builds

Changes in Dockerfile

• ARG statements are initialized with default params and as late as possible to avoid cache invalidation

• COPY statements combined to reduce layers

• RUN statements are sorted to get most caching for different builds

• Reference version of base dockerimage and also reference apt version to invalidate cache if new version is needed

• Limited nodejs support for plattforms where it is supported, some more work can be done here using a already existing nodejs image, but may it is better to run this in a separate docker server

• Usage of ARCH variable has changed, because ARCH itself isn't a common variable from buildx instead TARGETARCH is used

• [x] Integrationtest script runs against amd64 image

• [x] build script now uses buildx, buildx is installed if needed

• [x] Unittests are executed against amd64 image

• [x] Added dependabot script to detect changed base image

• [x] Build tow images vairiants using different layer options via separate action step

• [x] Build now uses the slim image from debian as docker base image

• [x] Build time reduced due to caching of fhem-svn and docker build cache

• [x] Upload docker image to github container registry

Todos not possible in this PR

• [ ] Finish upload image to docker hub., Needs to be done in the target repo with the needed rights
• [ ] Update Readme to instruct about available features per supported platform

Relates to: #28

[sidey79]

@jpawlowski

Did a lot of improvements. I think there is room left, but i think i now need some help to get correct push arguments for docker hub and later on update the readme

May we want to merge this into a feature branch instead of the dev branch to get the work done there

[sidey79]

@jpawlowski

Wie kommen wir hier weiter? Willst Du die Repo Rechte ggf. weitegeben?