Add bash auto-completion scripts

[fgiorgetti]

This is related to: #371

[agagliardi]

Is this feature already implemented? I tried to used source <(./skupper completion) but bash-5.2$ ./skupper <tab> fails with _get_comp_words_by_ref: command not found that seems something missing from Go Cobra

[hash-d]

@agagliardi, can you confirm you have the bash-completion package installed?

[agagliardi]

@agagliardi, can you confirm you have the bash-completion package installed? Yep. Package bash-completion-1:2.11-9.fc38.noarch is already installed