Add atty potential unsoundness (unaligned read) advisory

crates/atty/RUSTSEC-0000-0000.md

@@ -0,0 +1,21 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "atty"
+date = "2021-07-04"
+url = "https://github.com/softprops/atty/issues/50"
+categories = ["unaligned-read"]
+informational = "unsound"
+
+[affected]
+os = ["windows"]
+
+[versions]
+patched = []
+```
+
+# Potential unaligned read
+
+On windows, `atty` dereferences a potentially unaligned pointer.
+In practice however, the pointer won't be unaligned unless a custom global allocator is used.
+In particular, the `System` allocator on windows uses `HeapAlloc`, which guarantees a large enough alignment.