Create and link to upstream tracking issue

Author: saethlin

src/doc/src/reference/unstable.md

@@ -1674,8 +1674,9 @@ cargo-features = ["open-namespaces"]
 ## panic-immediate-abort
 
 * Tracking Issue: [#16042](https://github.com/rust-lang/cargo/issues/16042)
+* Upstream Tracking Issue: [rust-lang/rust#147286](https://github.com/rust-lang/rust/issues/147286)
 
-Allow use of the ImmediateAbort panic strategy in a Cargo profile
+Allow use of [`-Cpanic=immediate-abort`](doc.rust-lang.org/nightly/rustc/codegen-options/index.html#panic) through a Cargo profile
 
 This can be enabled like so:
 ```toml