chore(deps): update gatsby monorepo

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
babel-preset-gatsby	0.7.0 -> 0.8.0
gatsby (changelog)	2.27.5 -> 2.28.2
gatsby-image	2.6.0 -> 2.7.0
gatsby-plugin-feed	2.8.0 -> 2.9.0
gatsby-plugin-layout	1.5.0 -> 1.6.0
gatsby-plugin-netlify	2.6.0 -> 2.7.0
gatsby-plugin-react-helmet	3.5.0 -> 3.6.0
gatsby-plugin-sharp	2.7.1 -> 2.10.1
gatsby-plugin-typescript	2.7.0 -> 2.8.0
gatsby-remark-images	3.6.0 -> 3.7.1
gatsby-source-contentful	4.1.1 -> 4.2.1
gatsby-source-filesystem	2.6.1 -> 2.7.0
gatsby-transformer-remark	2.11.1 -> 2.12.0
gatsby-transformer-sharp	2.5.21 -> 2.8.0

---

Release Notes

gatsbyjs/gatsby

### [`v0.8.0`](https://togithub.com/gatsbyjs/gatsby/compare/v0.7.0...v0.8.0) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/v0.7.0...v0.8.0)

---

Renovate configuration

:date: Schedule: At any time (no schedule defined).

:vertical_traffic_light: Automerge: Disabled due to failing status checks.

:recycle: Rebasing: Renovate will not automatically rebase this PR, because other commits have been found.

:ghost: Immortal: This PR will be recreated if closed unmerged. Get config help if that's undesired.

---

• [ ] If you want to rebase/retry this PR, check this box

---

This PR has been generated by WhiteSource Renovate. View repository job log here.