chore: add changelog generator

tools/changelog.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+set -u
+
+error() {
+  echo >&2 "error: $*"
+  exit 1
+}
+
+command -v git > /dev/null || error "git command not found!"
+command -v git-chglog > /dev/null || error "git-chglog command not found!"
+
+changelog="CHANGELOG.md"
+tag="${tag:-$(git describe --abbrev=0 --tags || error "could not extract latest tag")}"
+
+if grep --quiet "<a name=\"$tag\"></a>" "$changelog"; then
+  error "changelog has already been generated for tag $tag!"
+fi
+
+cat <(git-chglog "$tag") "$changelog" > "$changelog.tmp"
+mv  "$changelog.tmp" "$changelog"
+
+if command -v npx > /dev/null; then
+  npx prettier --write "$changelog"
+fi