chore(deps): update gatsby monorepo

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
babel-preset-gatsby	devDependencies	minor	0.2.35 -> 0.3.0
gatsby	dependencies	minor	2.19.43 -> 2.20.2
gatsby-image	dependencies	minor	2.2.43 -> 2.3.0
gatsby-plugin-layout	dependencies	minor	1.1.23 -> 1.2.0
gatsby-plugin-manifest	dependencies	minor	2.2.47 -> 2.3.1
gatsby-plugin-offline	dependencies	minor	3.0.40 -> 3.1.0
gatsby-plugin-react-helmet	dependencies	minor	3.1.23 -> 3.2.0
gatsby-plugin-sharp	dependencies	minor	2.4.12 -> 2.5.1
gatsby-source-filesystem	dependencies	minor	2.1.55 -> 2.2.1
gatsby-transformer-sharp	dependencies	minor	2.3.18 -> 2.4.1

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Release Notes

gatsbyjs/gatsby

### [`v0.3.0`](https://togithub.com/gatsbyjs/gatsby/releases/0.3.0) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/2ff2ba395a86407e3ccfd1e010be7408a4817a82...7f197c0ac8f600a9a748992ffd5ebff19424d38a) [@​gesposito](https://togithub.com/gesposito) fixed up Gatsby's support for Babel in [#​31](https://togithub.com/gatsbyjs/gatsby/pull/31) as well as [converting the starter blog to ES6](https://togithub.com/gatsbyjs/gatsby-starter-blog/pull/1) Thanks! ### [`v0.2.36`](https://togithub.com/gatsbyjs/gatsby/compare/edb1423009c6a5cfc0e811331abde8716f07f306...2ff2ba395a86407e3ccfd1e010be7408a4817a82) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/edb1423009c6a5cfc0e811331abde8716f07f306...2ff2ba395a86407e3ccfd1e010be7408a4817a82)

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[codecov[bot]]

Codecov Report

Merging #84 into master will not change coverage by %. The diff coverage is n/a.

@@            Coverage Diff            @@
##            master       #84   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines            7         7           
=========================================
  Hits             7         7           

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