chore(scripts): add 'update-version.sh' script

scripts/update-versions.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+declare shell_targets=(setup.sh bpkg.sh)
+declare json_targets=(bpkg.json)
+declare latest="$(git describe --tags --abbrev=0)"
+
+for target in "${shell_targets[@]}"; do
+  sed -i "s/VERSION=.*/VERSION=\"$latest\"/g" "$target"
+done
+
+for target in "${json_targets[@]}"; do
+  sed -i "s/\"version\"\s*:\s*\".*\",/\"version\": \"$latest\",/g" "$target"
+done