Add atty potential unsoundness (unaligned read) advisory (#1462)

Co-authored-by: pinkforest <36498018+pinkforest@users.noreply.github.com>

crates/atty/RUSTSEC-0000-0000.md

@@ -0,0 +1,37 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "atty"
+date = "2021-07-04"
+url = "https://github.com/softprops/atty/issues/50"
+references = ["https://github.com/softprops/atty/pull/51", "https://github.com/softprops/atty/issues/57"]
+keywords = ["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.
+
+# atty is Unmaintained
+
+A Pull Request with a fix has been provided over a year ago but the maintainer seems to be unreachable.
+
+Last release of `atty` was almost 3 years ago.
+
+## Possible Alternative(s)
+
+The below list has not been vetted in any way and may or may not contain alternatives;
+
+ - [is-terminal](https://crates.io/crates/is-terminal)
+ - std::io::IsTerminal *nightly-only experimental*