Add note about MSRV compile failure.

README.md

@@ -22,6 +22,18 @@ This version of Parley has been verified to compile with **Rust 1.70** and later
 Future versions of Parley might increase the Rust version requirement.
 It will not be treated as a breaking change and as such can even happen with small patch releases.
 
+<details>
+<summary>Click here if compiling fails.</summary>
+
+As time has passed, some of Parley's dependencies could have released versions with a higher Rust requirement.
+If you encounter a compilation issue due to a dependency and don't want to upgrade your Rust toolchain, then you could downgrade the dependency.
+
+```sh
+# Use the problematic dependency's name and version
+cargo update -p package_name --precise 0.1.1
+```
+</details>
+
 ## Community
 
 Discussion of Parley development happens in the [Linebender Zulip](https://xi.zulipchat.com/), specifically the [#text stream](https://xi.zulipchat.com/#narrow/stream/205635-text).