chore(sveltekit): Update README with setup instructions (#7490)

Author: Lms24

packages/sveltekit/README.md

@@ -29,4 +29,105 @@ Currently, the minimum supported version of SvelteKit is `1.0.0`.
 
 This package is a wrapper around `@sentry/node` for the server and `@sentry/svelte` for the client, with added functionality related to SvelteKit.
 
-TODO: Add usage instructions
+## Usage
+
+Although the SDK is not yet stable, you're more than welcome to give it a try and provide us with early feedback.
+
+**Here's how to get started:**
+
+1. Ensure you've set up the [`@sveltejs/adapter-node` adapter](https://kit.svelte.dev/docs/adapter-node)
+
+2. Install the Sentry SvelteKit SDK:
+
+   ```bash
+   # Using npm
+   npm install @sentry/sveltekit
+
+   # Using yarn
+   yarn add @sentry/sveltekit
+   ```
+
+3. Create a `sentry.client.config.(js|ts)` file in the root directory of your SvelteKit project.
+   In this file you can configure the client-side Sentry SDK just like every other browser-based SDK:
+
+   ```javascript
+    import * as Sentry from '@sentry/sveltekit';
+
+    Sentry.init({
+      dsn: 'https://[email protected]/4504796902588416',
+
+      // For instance, initialize Session Replay:
+      replaysSessionSampleRate: 0.1,
+      replaysOnErrorSampleRate: 1.0,
+      integrations: [new Sentry.Replay()]
+    });
+   ```
+
+4. Add our `withSentryViteConfig` wrapper around your Vite config so that the Sentry SDK is added to your application in `vite.config.(js|ts)`:
+   ```javascript
+    import { sveltekit } from '@sveltejs/kit/vite';
+    import { withSentryViteConfig } from '@sentry/sveltekit';
+
+    export default withSentryViteConfig({
+      plugins: [sveltekit()],
+      // ...
+    });
+   ```
+
+5. Create a `sentry.server.config.(js|ts)` file in the root directory of your SvelteKit project.
+   In this file you can configure the server-side Sentry SDK, like the Sentry Node SDK:
+
+   ```javascript
+    import * as Sentry from '@sentry/sveltekit';
+
+    Sentry.init({
+      dsn: 'https://[email protected]/4504796902588416',
+    });
+   ```
+
+6. To catch errors in your `load` functions in `+page.(js|ts)`, wrap our `wrapLoadWithSentry` function:
+
+   ```javascript
+    import { wrapLoadWithSentry } from '@sentry/sveltekit';
+
+    export const load = wrapLoadWithSentry((event) => {
+      //...
+    });
+   ```
+
+7. In your `hooks.client.(js|ts)` or `hooks.server.(js|ts)`, you can wrap the `handleError` function as follows:
+
+   ```javascript
+    import { handleErrorWithSentry } from '@sentry/sveltekit';
+    import type { HandleClientError } from '@sveltejs/kit';
+
+    const myErrorHandler = ((input) => {
+      console.log('This is the client error handler');
+      console.log(input.error);
+    }) satisfies HandleClientError;
+
+    export const handleError = handleErrorWithSentry(myErrorHandler);
+
+    // or alternatively, if you don't have a custom error handler:
+    // export const handleError = handleErrorWithSentry();
+   ```
+
+## Known Limitations
+
+This SDK is still under active development and several features are missing.
+Take a look at our [SvelteKit SDK Development Roadmap](https://github.com/getsentry/sentry-javascript/issues/6692) to follow the progress:
+
+- **Performance monitoring** is not yet fully supported.
+  You can add the `BrowserTracing` integration but proper instrumentation for routes, page loads and navigations is still missing.
+  This will be addressed next, as we release the next alpha builds.
+
+- **Source Maps** upload is not yet working correctly.
+  We already investigated [some options](https://github.com/getsentry/sentry-javascript/discussions/5838#discussioncomment-4696985) but uploading source maps doesn't work automtatically out of the box yet.
+  This will be addressed next, as we release the next alpha builds.
+
+- **Adapters** other than `@sveltejs/adapter-node` are currently not supported.
+  We haven't yet tested other platforms like Vercel.
+  This is on our roadmap but it will come at a later time.
+
+- We're aiming to **simplify SDK setup** in the future so that you don't have to go in and manually add our wrappers to all your `load` functions and hooks.
+  This will be addressed once the SDK supports all Sentry features.