Add advisory for sequoia-openpgp (#1696)

Attacker-controlled input can lead to an out-of-bounds index, which
causes sequoia-openpgp to panic.  This has been fixed in versions
1.16.0, 1.8.1, and 1.1.1 of sequoia-openpgp.

crates/sequoia-openpgp/RUSTSEC-0000-0000.md

@@ -0,0 +1,25 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "sequoia-openpgp"
+date = "2023-05-16"
+url = "https://lists.sequoia-pgp.org/hyperkitty/list/announce@lists.sequoia-pgp.org/thread/SN2E3QRT4DMQ5JNEK6VIN6DJ5SH766DI/"
+references = ["https://gitlab.com/sequoia-pgp/sequoia/-/tags/openpgp%2Fv1.16.0"]
+categories = ["denial-of-service"]
+# Attacker-controlled input can result in a panic due to an
+# out-of-bounds array index.
+keywords = ["panic"]
+
+[versions]
+patched = [">= 1.1.1, < 1.2.0", ">= 1.8.1, < 1.9.0", ">= 1.16.0"]
+```
+
+# Out-of-bounds array access leads to panic
+
+Affected versions of the crate have several bugs where
+attacker-controlled input can result in the use of an out-of-bound
+array index.  Rust detects the use of the out-of-bound index and
+causes the application to panic.  An attacker may be able to use this
+to cause a denial-of-service.  However, it is not possible for an
+attacker to read from or write to the application's address space.
+