[ADD]Airbrake-js installtion instruction in svelte framework

packages/browser/examples/svelte/README.md

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+# Usage with Svelte
+
+Integration with Svelte is as simple as adding `handleError` hooks (Server or Client):
+
+- For server error handling, add `handleError` of `HandleServerError` type
+- For handle error of client add `handleError` of `HandleClientError` type
+
+## App configuration
+
+```ts
+// app.d.ts
+
+// Add interface of Error
+
+// See https://kit.svelte.dev/docs/types#app
+// for information about these interfaces
+// and what to do when importing types
+declare global {
+  namespace App {
+    interface Error {
+      message: unknown;
+      errorId: string;
+    }
+  }
+}
+
+export {};
+```
+
+## Server Hook
+
+To establish an error handler for the server, use a `Notifier` with your `projectId` and `projectKey` as parameters. In this case, the handler will be located in the file `src/hooks.server.js`.
+
+```js
+// src/hooks.server.js
+import crypto from 'crypto';
+import { Notifier } from '@airbrake/browser';
+
+var airbrake = new Notifier({
+  projectId: 1, // Airbrake project id
+  projectKey: 'FIXME', // Airbrake project API key
+});
+
+airbrake.addFilter(function (notice) {
+  notice.context.hooks = 'server';
+  return notice;
+});
+
+/** @type {import('@sveltejs/kit').HandleServerError} */
+export function handleError({ error, event }) {
+  const errorId = crypto.randomUUID();
+  // example integration with https://airbrake.io/
+  airbrake.notify({
+    error: error,
+    params: { errorId: errorId, event: event },
+  });
+
+  return {
+    message: error,
+    errorId,
+  };
+}
+```
+
+## Client Hook
+
+To establish an error handler for the client, use a `Notifier` with your `projectId` and `projectKey` as parameters. In this case, the handler will be located in the file `src/hooks.client.js`.
+
+```js
+// src/hooks.client.js
+import crypto from 'crypto';
+import { Notifier } from '@airbrake/browser';
+
+var airbrake = new Notifier({
+  projectId: 1, // Airbrake project id
+  projectKey: 'FIXME', // Airbrake project API key
+});
+
+airbrake.addFilter(function (notice) {
+  notice.context.hooks = 'client';
+  return notice;
+});
+
+/** @type {import('@sveltejs/kit').HandleClientError} */
+export function handleError({ error, event }) {
+  const errorId = crypto.randomUUID();
+  // example integration with https://airbrake.io/
+  airbrake.notify({
+    error: error,
+    params: { errorId: errorId, event: event },
+  });
+
+  return {
+    message: error,
+    errorId,
+  };
+}
+```
+
+## Test
+
+To test that server hook has been installed correctly in your Svelte project.
+
+```js
+// +page.server.js
+
+import { error } from '@sveltejs/kit';
+import * as db from '$lib/server/database';
+
+/** @type {import('./$types').PageServerLoad} */
+export async function load({ params }) {
+  const post = await db.getPost(params.slug);
+
+  if (!post) {
+    throw error(404, {
+      message: 'Not found',
+    });
+  }
+
+  return { post };
+}
+```
+
+To test that client hook has been installed correctly in your Svelte project, just open up the JavaScript console in your internet browser and paste in:
+
+```js
+window.onerror('TestError: This is a test', 'path/to/file.js', 123);
+```