feat: add support for nixpacks as a builder

Closes #5338

plugins/builder-nixpacks/install

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/property-functions"
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
+
+trigger-builder-nixpacks-install() {
+  declare desc="installs the builder-nixpacks plugin"
+  declare trigger="install"
+
+  fn-plugin-property-setup "builder-nixpacks"
+
+  mkdir -p "${DOKKU_LIB_ROOT}/data/builder-nixpacks"
+  chown -R "${DOKKU_SYSTEM_USER}:${DOKKU_SYSTEM_GROUP}" "${DOKKU_LIB_ROOT}/data/builder-nixpacks"
+}
+
+trigger-builder-nixpacks-install "$@"