feat: Add automated Raspberry Pi build action

[MoJo2600]

Added a github action to build Raspberry Pi images with docker buildx

Current state:

• The build works and produces a binary (See: https://github.com/MoJo2600/welle.io/actions/runs/4957542506
• Currently the generated build output is stored as an artifact, but there is no further processing / releasing
• I did not test the binary yet

fixes #781

What does this PR do and why is it necessary?

How was it tested? How can it be tested by the reviewer?

Any background context you want to provide?

What are the relevant tickets if any?

Screenshots (if appropriate)

Further notes

[tenzap]

Just wondering, are you building the next branch or the master branch.

I see references to qt5, while next branch AFAIK now required Qt6.

The required build dependencies for qt6 are:

cmake libairspy-dev libasound2-dev libfaad-dev libfftw3-dev libmp3lame-dev libmpg123-dev libpulse-dev libqt6opengl6-dev librtlsdr-dev libsoapysdr-dev qt6-base-dev qt6-charts-dev qt6-declarative-dev qt6-multimedia-dev

And depending on their version you may also need these:

qml6-module-qtcharts  qml6-module-qtquick3d-spatialaudio

Logic to determine if they are required is:

            if dpkg --compare-versions $(dpkg-query -W qt6-charts-dev | cut -d "	" -f 2) lt 6.4.2-3; then
              sudo apt-get -y install qml6-module-qtcharts
            fi
            if dpkg --compare-versions $(dpkg-query -W qt6-multimedia-dev | cut -d "	" -f 2) lt 6.4.2-5; then
              sudo apt-get -y install qml6-module-qtquick3d-spatialaudio
            fi

You may want to have a look at
https://github.com/tenzap/welle.io/blob/next-035-qt651/.github/workflows/linux.yml
if it is newer than
https://github.com/AlbrechtL/welle.io/blob/next/.github/workflows/linux.yml

[MoJo2600]

Thanks for the info! I was building the next branch, but I will incorporate the packages you mentioned.

[AlbrechtL]

Sorry for the really long reply and thanks for you pull request.

[AlbrechtL]

@MoJo2600 Can you update the README.md in order how to use this docker image.

[MoJo2600]

@AlbrechtL I'm currently working on it. I also updated all the dependencies as well but I want to test the resulting binary on my pies first.

[AlbrechtL]

Great!