feat: Require list of expected algorithms when secret/publicKey is given

[codedust]

Summary

Instead of allowing only one single algorithm during signature validation, one can now specify a comma-separated list of algorithms using the --algs command line parameter.

In order to encourage users to be aware of the choice of algorithms and safely define a subset of the supported algorithms, the --algs parameter is now required when the -S parameter is set.

Preflight checklist

• [x] Code formatted with rustfmt
• [x] Relevant tests added
• [x] Any new documentation added (documentation of command line parameters has been updated)

Closes #134.

[codedust]

Rebased to main