Mesh repository

@sloede and I just had a discussion about a possible way for a Trixi mesh library. A possible way forward could be to create a new repo in the Trixi framework. For each mesh, we would add a new folder containing a README.md, possibly a LICENSE.md, and mesh source files (such as control files for HOHQMesh). The generated mesh files can be added as binary artifacts to manually drafted releases whenever a new mesh is added. Then, we can use the Julia artifact system to get the binaries locally.

Review the proposed repository structure: one folder per mesh with README.md, optional LICENSE.md, and mesh source files such as HOHQMesh control files. Then examine how Julia's artifact system would provide generated mesh binaries locally. Done means the repository structure, artifact distribution approach, and release process are defined and agreed upon; no implementation files or tests are identified in the issue.

Written by the indexing model from the issue text.