added pre-commit hook to ensure changelog was updated

.githooks/pre-push

@@ -0,0 +1,8 @@
+#!/bin/sh
+command -v git-lfs >/dev/null 2>&1 || { echo >&2 "\nThis repository is configured for Git LFS but 'git-lfs' was not found on your path. If you no longer wish to use Git LFS, remove this hook by deleting the 'pre-push' file in the hooks directory (set by 'core.hookspath'; usually '.git/hooks').\n"; exit 2; }
+git lfs pre-push "$@"
+
+if ! git status -s | grep -q "M Changelog.md"; then
+    echo "The changelog was not updated. Please document your changes in Changelog.md before pushing."
+    exit 1
+fi