Delete submit-a-blogpost.md
Delete submit-a-blogpost.md

This doc is redundant since "How to Contribute" already explains how to submit a change.
0x80/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,0x80/gatsby,ChristopherBiscardi/gatsby,mingaldrichgan/gatsby,0x80/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,mingaldrichgan/gatsby