Add @probo/cookie-banner SDK package scaffold

Introduce the boilerplate for a new public npm package that will
serve as the cookie consent banner JavaScript SDK. The package
uses esbuild to produce both an IIFE bundle (for script tag
embedding) and an ESM module. Versioning is independent from the
monorepo: CI compares package.json against npm and only publishes
when the version changes.

Signed-off-by: Émile Ré <emile@getprobo.com>

packages/cookie-banner/build.mjs

@@ -0,0 +1,36 @@
+// Copyright (c) 2025-2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+import * as esbuild from "esbuild";
+
+const shared = {
+  entryPoints: ["src/index.ts"],
+  bundle: true,
+  target: "es2020",
+};
+
+await Promise.all([
+  esbuild.build({
+    ...shared,
+    outfile: "dist/cookie-banner.iife.js",
+    format: "iife",
+    globalName: "ProboCookieBanner",
+    minify: true,
+  }),
+  esbuild.build({
+    ...shared,
+    outfile: "dist/cookie-banner.mjs",
+    format: "esm",
+  }),
+]);