remove manually created typing d ts file (#249)

* Rename file

".d.ts" files are files that are automatically generated during compilation (in case option is set) and shouldn't be created manually.

* Export types and interfaces

* Add missing imports

src/components/SourceCard.tsx

@@ -16,6 +16,7 @@ import React from 'react';
 import { Link, useHistory } from 'react-router-dom';
 import { langCodeToName } from 'util/language';
 import useLocalStorage from 'util/useLocalStorage';
+import { ISource } from 'typings';
 
 const MobileWidthButtons = styled('div')(({ theme }) => ({
     display: 'flex',