fix: raw JWKS --secret for ES256/ES384 alg

[vdbulcke]

Summary

Fix passing raw JWKS as --secret (e.g. --secret "$(curl https://auth.domain.com/jwks.json)") for ES256/ES384 alg.

Relates to https://github.com/mike-engel/jwt-cli/pull/299.

Preflight checklist

• [X] Code formatted rustfmt ($ cargo fmt)
• [X] Code linter check with clippy ($ cargo clippy)
• [X] Relevant tests added
• [X] Any new documentation added