feat(docs): add bitwarden to TOC iin README

Author: gorillamoe

README.md

@@ -46,6 +46,7 @@ Azure Key Vault, OpenBao, and Bitwarden Secrets Manager to your application
   - [AWS Secrets Manager](#aws-secrets-manager)
   - [Azure Key Vault](#azure-key-vault)
   - [OpenBao](#openbao)
+  - [Bitwarden Secrets Manager](#bitwarden-secrets-manager-bitwarden)
 
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