refactor(packages): change package structure

packages/react/src/custom.d.ts

@@ -0,0 +1,13 @@
+declare module '*.css' {
+  const content: { [className: string]: string };
+  export default content;
+}
+
+type SvgrComponent = React.FunctionComponent<React.SVGAttributes<SVGElement>>;
+
+declare module '*.svg' {
+  const svgUrl: string;
+  const svgComponent: SvgrComponent;
+  export default svgUrl;
+  export { svgComponent as ReactComponent };
+}