We should add a naming convention that specifies minimum length for free function names

[jbigot]

I believe we should add a naming convention that specifies that this is way too short for a free function name

Originally posted by @jbigot in https://github.com/CExA-project/ddc/pull/121#discussion_r1510706639

[tpadioleau]

see https://releases.llvm.org/14.0.0/tools/clang/tools/extra/docs/clang-tidy/checks/readability-identifier-length.html but it seems to only apply to variables