title: How do I add a typings.d.ts file to an Angular 7 project?
body: <p>I am following this <a href="https://alligator.io/angular/stripe-elements/" rel="noreferrer">tutorial here</a>, and the author says to add two declarations to the project's <code>typings.d.ts</code> file. However, when using the <code>ng-cli</code> to create the Angular 7 project, there is no such file generated. </p>
  
  <p>In <a href="https://www.bennadel.com/blog/3169-adding-custom-typings-files-d-ts-in-an-angular-2-typescript-application.htm" rel="noreferrer">this other article</a> (for Angular 2), the author suggests to create a <code>typings</code> folder and place the <code>typings.d.ts</code> there and to modify the <code>tsconfig.json</code> file with a <code>files</code> key; doing this gives me a <code>TS5023: Uknown compiler option 'files'.</code> message.</p>
  
  <p>Yet, in this <a href="https://stackoverflow.com/questions/44836379/add-custom-typings-files-to-angular-cli">post</a>, the top answer suggest that <code>typings.d.ts</code> should have been created with <code>ng-cli</code> under the <code>src</code> folder, but I don't see it (I am using Angular CLI v7.3.1).</p>
  
  <p>My question is, for Angular 7, how and where do I add <code>typings.d.ts</code>? What other files do I need to modify when adding such file?</p>