doc(svelte): Add usage and sourcemaps instructions to README (#5544)

Add content to the Readme of the Svelte SDK:

1. Badges for the Svelte SDK (will only work once we publish the package on NPM)
2. A disclaimer saying that the SDK is in alpha and that it only supports Svelte (not SvelteKit) for the time being
3. Basic usage instructions (i.e. where and how to init the SDK) + a link to the Browser SDK docs
4. Basic sourcemaps upload instructions

Author: Lms24

packages/svelte/README.md

@@ -6,4 +6,66 @@
 
 # Official Sentry SDK for Svelte
 
-This SDK is work in progress, and should not be used before officially released.
+[![npm version](https://img.shields.io/npm/v/@sentry/svelte.svg)](https://www.npmjs.com/package/@sentry/svelte)
+[![npm dm](https://img.shields.io/npm/dm/@sentry/svelte.svg)](https://www.npmjs.com/package/@sentry/svelte)
+[![npm dt](https://img.shields.io/npm/dt/@sentry/svelte.svg)](https://www.npmjs.com/package/@sentry/svelte)
+[![typedoc](https://img.shields.io/badge/docs-typedoc-blue.svg)](http://getsentry.github.io/sentry-javascript/)
+
+This SDK is considered **experimental and in an alpha state**. It may experience breaking changes. Please reach out on [GitHub](https://github.com/getsentry/sentry-javascript/issues/new/choose) if you have any feedback or concerns. This SDK currently only supports [Svelte](https://svelte.dev/) and is not yet officially compatible with with [SvelteKit](https://kit.svelte.dev/).
+
+## General
+
+This package is a wrapper around `@sentry/browser`, providing error monitoring and basic performance monitoring
+features for [Svelte](https://svelte.dev/).
+
+To use the SDK, initialize Sentry in your Svelte entry point `main.js` before you bootstrap your Svelte app:
+
+```ts
+// main.js / main.ts
+
+import App from "./App.svelte";
+
+import * as Sentry from "@sentry/svelte";
+import { BrowserTracing } from "@sentry/tracing";
+
+// Initialize the Sentry SDK here
+Sentry.init({
+  dsn: "__DSN__",
+  release: "my-project-name@2.3.12",
+  integrations: [new BrowserTracing()],
+
+  // Set tracesSampleRate to 1.0 to capture 100%
+  // of transactions for performance monitoring.
+  // We recommend adjusting this value in production
+  tracesSampleRate: 1.0,
+});
+
+// Then bootstrap your Svelte app
+const app = new App({
+  target: document.getElementById("app"),
+});
+
+export default app;
+```
+
+The Sentry Svelte SDK supports all features from the `@sentry/browser` SDK. Until it becomes more stable, please refer to the Sentry [Browser SDK documentation](https://docs.sentry.io/platforms/javascript/) for more information and usage instructions.
+
+## Sourcemaps and Releases
+
+To [create releases and upload source maps](https://docs.sentry.io/platforms/javascript/sourcemaps/uploading/cli/) to Sentry, we recommend using [`sentry-cli`](https://github.com/getsentry/sentry-cli). You can create a bash script to take care of creating a release, uploading source maps and finalizing the release:
+
+```bash
+#!/bin/bash
+
+VERSION=<your version>
+ORG=<your org-slug>
+PROJECT=<your project-slug>
+
+SOURCEMAPS_PATH=./dist
+
+sentry-cli releases new $VERSION --org $ORG --project $PROJECT
+sentry-cli releases files $VERSION upload-sourcemaps $SOURCEMAPS_PATH --org $ORG --project $PROJECT
+sentry-cli releases finalize $VERSION  --org $ORG --project $PROJECT
+```
+
+Please note that the paths provided in this example work for a typical Svelte project that adheres to the project structure set by [create-vite](https://www.npmjs.com/package/create-vite) with the `svelte(-ts)` template. If your project setup differs from this template, your configuration may need adjustments. Please refer to our documentation of [Advanced `sentry-cli` Sourcemaps Options](https://docs.sentry.io/product/cli/releases/#sentry-cli-sourcemaps) and to our [Sourcemaps Troubleshooting Guide](https://docs.sentry.io/platforms/javascript/sourcemaps/troubleshooting_js/).