create-react-app/packages/react-scripts/config/react-app.d.ts

// @remove-file-on-eject
// Do not edit this file. It's replaced every time you launch a toolbox action.
// If you need to add additional declarations, please do so in a new file.

declare module '*.json' {
  const value: any;
  export default value;
}

declare module '*.bmp' {
  const src: string;
  export default src;
}

declare module '*.gif' {
  const src: string;
  export default src;
}

declare module '*.jpg' {
  const src: string;
  export default src;
}

declare module '*.jpeg' {
  const src: string;
  export default src;
}

declare module '*.png' {
  const src: string;
  export default src;
}

declare module '*.svg' {
  import React = require('react');

  export const ReactComponent: React.SFC<React.SVGProps<SVGSVGElement>>;

  const src: string;
  export default src;
}

declare module '*.module.css' {
  const classes: { [key: string]: string };
  export default classes;
}

declare module '*.module.scss' {
  const classes: { [key: string]: string };
  export default classes;
}

declare module '*.module.sass' {
  const classes: { [key: string]: string };
  export default classes;
}