Improved markdown (#9888)

Improved markdown - for correct displaying link

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docs/blog/2018-08-09-swag-store/index.md

@@ -78,3 +78,4 @@ Thanks for being part of the open source community! 💪💜
 [auth0]: https://auth0.com/
 [invite]: https://github.com/gatsbyjs/peril-gatsbyjs/blob/master/org/invite-collaborator.ts
 [peril]: https://github.com/danger/peril
+[contribute]: /docs/how-to-contribute/