doc: Add ABI checking with check-abi.sh to the Release Process

doc/release-process.md

@@ -34,6 +34,11 @@ build=$(mktemp -d)
 cmake -B $build -DCMAKE_INSTALL_PREFIX=$dir && cmake --build $build --target install && ls -RlAh $dir
 gcc -o ecdsa examples/ecdsa.c -I $dir/include -L $dir/lib*/ -l secp256k1 -Wl,-rpath,"$dir/lib",-rpath,"$dir/lib64" && ./ecdsa
 ```
+4. Use the [`check-abi.sh`](/tools/check-abi.sh) tool to ensure there are no unexpected ABI incompatibilities and that the version number and release notes accurately reflect all potential ABI changes. To run this tool, the `abi-dumper` and `abi-compliance-checker` packages are required.
+
+```shell
+tools/check-abi.sh
+```
 
 ## Regular release