Update gatsby monorepo

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby	dependencies	minor	2.18.25 -> 2.19.5
gatsby-plugin-sharp	dependencies	minor	2.3.13 -> 2.4.0

---

Release Notes

gatsbyjs/gatsby

### [`v2.19.5`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.4...gatsby@2.19.5) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.4...gatsby@2.19.5) ### [`v2.19.4`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.3...gatsby@2.19.4) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.3...gatsby@2.19.4) ### [`v2.19.3`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.2...gatsby@2.19.3) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.2...gatsby@2.19.3) ### [`v2.19.2`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.1...gatsby@2.19.2) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.1...gatsby@2.19.2) ### [`v2.19.1`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.0...gatsby@2.19.1) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.19.0...gatsby@2.19.1) ### [`v2.19.0`](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.25...gatsby@2.19.0) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/gatsby@2.18.25...gatsby@2.19.0)

---

Renovate configuration

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

:vertical_traffic_light: Automerge: Disabled by config. Please merge this manually once you are satisfied.

:recycle: Rebasing: Whenever PR becomes conflicted, or if you tick the rebase/retry checkbox below.

: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.