Add "The Twelve-Factor App"

Author: alinnert

src/links.json

@@ -441,6 +441,11 @@
           "searchUrl": "https://cheatsheetseries.owasp.org/?q={search}",
           "searchConcat": "%20"
         },
+        {
+          "title": "The Twelve-Factor App",
+          "url": "https://12factor.net",
+          "description": "A methodology for building modern, scalable, maintainable software-as-a-service apps."
+        },
         {
           "title": "Keep a Changelog",
           "url": "https://keepachangelog.com/en/1.1.0",