feat: upgrade Gatsby plugin to v2

[ascorbic]

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Are you adding a plugin or updating one?

• Adding a plugin
• Updating a plugin

Have you completed the following?

• Read and followed the plugin author guidelines.
• Included all required fields in your entry.
• Tested the plugin locally and on Netlify, using the plugin version stated in your entry.

Test plan
Please add a link to a successful public deploy log using the stated version of the plugin. Include any other context reviewers might need for testing.

[ehmicky]

🎉 🎉 🎉