Bundle build scripts should be more easily found

[yorikvanhavre]

Is there an existing issue for this?

• I have searched the existing issues

Problem description

As a follow-up of #13871, the location of the bundle build scripts and their documentation should be indicated in the FreeCAD README file to be more easily found by users

Full version info

n/a

Subproject(s) affected?

None

Anything else?

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[adrianinsaval]

I will prepare a document describing the build steps and then we can reference that either in the main readme or in a readme in tools/build

[yorikvanhavre]

There is already some docs at https://freecad.github.io/DevelopersHandbook/technical/ReleasePackages.html