Update mls.json

adding public-security

Author: simoneonofri

mls.json

@@ -1718,6 +1718,22 @@
       "topic": "WebAuthn"
     }
   },
+  "[email protected]": {
+    "w3c/securityig": {
+      "events": [
+        "issues.opened",
+        "issues.closed",
+        "issue_comment.created",
+        "pull_request.opened",
+        "pull_request.closed",
+        "push"
+      ]
+    },
+    "digest:tuesday": {
+      "repos": ["w3c/securityig"],
+      "topic": "Security"
+    }
+  },
   "[email protected]": {
     "w3c/csswg-drafts": {
       "events": [