package maintenance

- update to TS6
- replace ncc by rollup, which seems to now be the recommended workflow according to <https://github.com/actions/typescript-action>
- remove buildjet provider, as they are shutting down, see <https://buildjet.com/for-github-actions/blog/we-are-shutting-down>

rollup.config.ts

@@ -0,0 +1,24 @@
+// import * as fs from "node:fs";
+
+import commonjs from "@rollup/plugin-commonjs";
+import json from "@rollup/plugin-json";
+import nodeResolve from "@rollup/plugin-node-resolve";
+import type { RollupWatchOptions } from "rollup";
+
+// const pkg = JSON.parse(fs.readFileSync("./package.json", { encoding: "utf-8" }));
+// const external = ["node:module", "node:path", "node:fs", "node:fs/promises", "typescript", "rollup", "@babel/code-frame", "magic-string", "@jridgewell/remapping", "@jridgewell/sourcemap-codec", "convert-source-map"];
+
+const config: Array<RollupWatchOptions> = [
+  {
+    input: "./.build/src/restore.js",
+    output: { file: "./dist/restore.js", format: "es" },
+    plugins: [nodeResolve({ preferBuiltins: true }), commonjs(), json()],
+  },
+  {
+    input: "./.build/src/save.js",
+    output: { file: "./dist/save.js", format: "es" },
+    plugins: [nodeResolve({ preferBuiltins: true }), commonjs(), json()],
+  },
+];
+
+export default config;