message: Update Angular installation instructions
  This adds a comment with the file path in each code block in Angular
  installation instructions. This is mainly to better guide our users.
diff: ### Create an error handler
  The first step is to create an error handler with a `Notifier`
  initialized with your `projectId` and `projectKey`. In this example the
  -handler will be in a file called `error_handler.ts`.
  +handler will be in a file called `airbrake-error-handler.ts`.
  ```ts
  +// src/app/airbrake-error-handler.ts
  +
  import { ErrorHandler } from '@angular/core';
  import { Notifier } from '@airbrake/browser';
  @@ -28,15 +30,17 @@ export class AirbrakeErrorHandler implements ErrorHandler {
  ### Add the error handler to your `AppModule`
  -The last step is adding the `ErrorHandler` to your `AppModule`, then your app
  -will be ready to report errors to Airbrake.
  +The last step is adding the `AirbrakeErrorHandler` to your `AppModule`, then
  +your app will be ready to report errors to Airbrake.
  ```ts
  +// src/app/app.module.ts
  +
  import { BrowserModule } from '@angular/platform-browser';
  import { NgModule, ErrorHandler } from '@angular/core';
  import { AppComponent } from './app.component';
  -import { AirbrakeErrorHandler } from './error_handler';
  +import { AirbrakeErrorHandler } from './airbrake-error-handler';
  @NgModule({
  declarations: [
  