fix: upgrade multiple dependencies with Snyk

Snyk has created this PR to upgrade:
  - gatsby from 2.19.28 to 2.32.13.
    See this package in npm: https://www.npmjs.com/package/gatsby
  - gatsby-image from 2.2.42 to 2.11.0.
    See this package in npm: https://www.npmjs.com/package/gatsby-image
  - gatsby-plugin-google-analytics from 2.1.33 to 2.11.0.
    See this package in npm: https://www.npmjs.com/package/gatsby-plugin-google-analytics
  - gatsby-plugin-manifest from 2.2.42 to 2.12.1.
    See this package in npm: https://www.npmjs.com/package/gatsby-plugin-manifest
  - gatsby-plugin-offline from 3.0.35 to 3.10.2.
    See this package in npm: https://www.npmjs.com/package/gatsby-plugin-offline
  - gatsby-source-filesystem from 2.1.46 to 2.11.1.
    See this package in npm: https://www.npmjs.com/package/gatsby-source-filesystem
  - gatsby-transformer-json from 2.2.25 to 2.11.0.
    See this package in npm: https://www.npmjs.com/package/gatsby-transformer-json

See this project in Snyk:
https://app.snyk.io/org/mjperrins/project/2a447513-0570-44cb-b9fb-4a2006d8a651?utm_source=github&utm_medium=referral&page=upgrade-pr