feat: add css parameter for custom CSS injection in screenshots

sdk/node/README.md

@@ -103,17 +103,21 @@ const singleHide = await snap.capture('https://example.com', {
 });
 ```
 
-### Combined Dark Mode + Element Hiding
+### Custom CSS Injection
 
 ```typescript
-// Perfect for clean marketing screenshots
-const marketingShot = await snap.capture({
-  url: 'https://your-saas-app.com',
+// Inject custom CSS before capture
+const styled = await snap.capture({
+  url: 'https://example.com',
+  css: 'body { background: #1a1a2e !important; color: #eee !important; font-family: "Comic Sans MS" }',
+});
+
+// Combine with other options
+const combined = await snap.capture({
+  url: 'https://example.com',
+  css: '.hero { padding: 80px 0 } h1 { font-size: 48px }',
   darkMode: true,
-  hideSelectors: ['.dev-banner', '.beta-notice'],
-  width: 1920,
-  height: 1080,
-  deviceScale: 2,
+  hideSelectors: ['.cookie-banner'],
 });
 ```
 
@@ -145,6 +149,7 @@ Returns a `Promise<Buffer>` containing the screenshot image.
 | `waitUntil` | `string` | `'domcontentloaded'` | Load event to wait for |
 | `darkMode` | `boolean` | `false` | Emulate prefers-color-scheme: dark |
 | `hideSelectors` | `string \| string[]` | — | CSS selectors to hide before capture |
+| `css` | `string` | — | Custom CSS to inject before capture (max 5000 chars) |
 
 ### `snap.health()`