feat: add source to footer

src/components/Footer/index.tsx

@@ -1,4 +1,5 @@
 import React, { FC } from "react"
+import packageJson from "../../../package.json"
 import { Container } from "../Container"
 import * as SC from "./styles"
 
@@ -9,7 +10,8 @@ export const Footer: FC = () => {
         <p>
           © {new Date().getFullYear()}, Built with
           {` `}
-          <a href="https://www.gatsbyjs.org">Gatsby</a>
+          <a href="https://www.gatsbyjs.org">Gatsby</a> - Source on{" "}
+          <a href={packageJson.repository.url}>GitHub</a>
         </p>
       </Container>
     </SC.FooterWrapper>