Re commercialhaskell#6490 Update release guide for backward compatability

Author: mpilgrem

doc/maintainers/releases.md

@@ -67,26 +67,29 @@ Examples:
 
 4.  Check the copyright dates, and update if needed.
 
-5.  Ensure CI matrices in docs (travis-complex, appveyor, azure) have current
+5.  Check the backwards compatability section of `CONTRIBUTING.md` is up to
+    date.
+
+6.  Ensure CI matrices in docs (travis-complex, appveyor, azure) have current
     stackage snapshots and GHC versions (e.g.
     https://github.com/commercialhaskell/stack/pull/4565/files)
 
-6.  Update any `stack-*.yaml` that uses a `nightly` snapshot to the latest
+7.  Update any `stack-*.yaml` that uses a `nightly` snapshot to the latest
     nightly (go over the extra-deps too) and ensure the project builds and tests
     pass. For example, command:
 
     ~~~text
     stack build --stack-yaml=… --haddock --test --bench --no-run-benchmarks
     ~~~
 
-7.  The Windows installer is built using an
+8.  The Windows installer is built using an
     [NSIS compiler](https://nsis.sourceforge.io/Main_Page). Check that the NSIS
     compiler that will be used is capable of handling
     [large strings](https://nsis.sourceforge.io/Special_Builds).
 
-8.  Ensure the integration tests pass on Linux, macOS and Windows.
+9.  Ensure the integration tests pass on Linux, macOS and Windows.
 
-9.  Some people prefer, or need, to build Stack with Cabal (the tool). Check
+10. Some people prefer, or need, to build Stack with Cabal (the tool). Check
     that `cabal.project` is up to date (the specified `with-compiler:`). Check
     that `cabal.config` is up to date and is not missing dependencies relevant
     on Windows and non-Windows operating systems, following the instructions in