Release 0.6.1

[nihaopaul]

Bumps version to 0.6.1.

Changes since 0.6.0:

• refactor: change audience representation from Vec<String> to Arc<HashSet<String>> for improved performance (fix: eliminate per-request audience catalog copy (CWE-400) #47)
• chore(deps): bump jsonwebtoken from 10.4.0 to 11.0.0 (chore(deps): bump jsonwebtoken from 10.4.0 to 11.0.0 #45)
• chore(deps): bump base64 from 0.22.1 to 0.23.1 (chore(deps): bump base64 from 0.22.1 to 0.23.1 #44)
• ci: hold rand at 0.8 until rsa 0.10 is stable (ci: hold rand at 0.8 until rsa 0.10 is stable #46)
• docs: recommend credential-free per-app setup (docs: recommend credential-free per-app setup #42)