docs: update README with usage instructions for nativescript-supabase

Author: edusperoni

packages/nativescript-supabase/README.md

@@ -6,7 +6,59 @@ npm install @edusperoni/nativescript-supabase
 
 ## Usage
 
-// TODO
+This plugin makes `@supabase/supabase-js` work in NativeScript.
+
+It does two things for you:
+
+- Adds NativeScript-compatible build replacements through `nativescript.webpack.js`.
+- Polyfills browser APIs needed by Supabase when you import the plugin:
+	- `localStorage` (backed by NativeScript `ApplicationSettings`)
+	- `WebSocket` (via `@valor/nativescript-websockets`)
+
+After that, just use the official Supabase JS client.
+
+### 1) Install
+
+```bash
+npm install @edusperoni/nativescript-supabase @supabase/supabase-js
+```
+
+### 2) Import once at app startup
+
+Import this package **before** creating your Supabase client.
+
+```ts
+import '@edusperoni/nativescript-supabase';
+```
+
+Place it in your app entry file (for example, `app.ts` / `main.ts`) so it runs once on startup.
+
+### 3) Use Supabase normally
+
+```ts
+import '@edusperoni/nativescript-supabase';
+import { createClient } from '@supabase/supabase-js';
+
+const supabaseUrl = 'https://YOUR_PROJECT_ID.supabase.co';
+const supabaseAnonKey = 'YOUR_SUPABASE_ANON_KEY';
+
+export const supabase = createClient(supabaseUrl, supabaseAnonKey);
+
+async function loadProfile() {
+	const { data, error } = await supabase.from('profiles').select('*').limit(1);
+	if (error) {
+		console.error(error);
+		return;
+	}
+	console.log(data);
+}
+```
+
+## Notes
+
+- No extra manual polyfill setup is required beyond importing `@edusperoni/nativescript-supabase`.
+- `localStorage` persistence maps to NativeScript app settings storage.
+- Supabase usage (auth, realtime, queries, storage client APIs) follows the standard `@supabase/supabase-js` documentation.
 
 ## License