Clean up and document project files (#4560)

.github/SECURITY.md

@@ -2,4 +2,24 @@
 
 ## Reporting a Vulnerability
 
-Usually, all issues are tracked publicly on [GitHub](https://github.com/nlohmann/json/issues). If you want to make a private report (e.g., for a vulnerability or to attach an example that is not meant to be published), please send an email to <mail@nlohmann.me>. You can use [this key](https://keybase.io/nlohmann/pgp_keys.asc?fingerprint=797167ae41c0a6d9232e48457f3cea63ae251b69) for encryption.
+We value the security of our users and appreciate your efforts to responsibly disclose vulnerabilities. If you have
+identified a security vulnerability in this repository, please use the GitHub Security Advisory
+["Report a Vulnerability"](https://github.com/nlohmann/json/security/advisories/new) tab.
+
+Until it is published, this draft security advisory will only be visible to the maintainers of this project. Other
+users and teams may be added once the advisory is created.
+
+We will send a response indicating the next steps in handling your report. After the initial reply to your report, we
+will keep you informed of the progress towards a fix and full announcement and may ask for additional information or
+guidance.
+
+For vulnerabilities in third-party dependencies or modules, please report them directly to the respective maintainers.
+
+## Additional Resources
+
+- Explore security-related topics and contribute to tools and projects through
+  [GitHub Security Lab](https://securitylab.github.com/).
+- Learn more about responsible disclosure and reporting vulnerabilities in GitHub at
+  [About coordinated disclosure of security vulnerabilities](https://docs.github.com/en/code-security/repository-security-advisories/about-coordinated-disclosure-of-security-vulnerabilities).
+
+We sincerely thank you for contributing to the security and integrity of this project!