Upgrade gatsby plugin to support V3

[Dkendal]

Update's the peer dep of the Gatsby plugin so that it doesn't cause warnings with Gatsby 3. Fixes some audit warnings with the package. Makes an update to one of the Gatsby examples to use the updated version.

• chore(gatsby-minimal-starter): upgrade gatsby plugin
• chore(gatsby-minimal-starter): bump gatsby to v3
• fix(gatsby-minimal-starter): fix webpack compilation
• feat(gatsby): add V3 support
• fix(gatsby): run npm audit fix
• feat(gatsby): upgrade dev dep to gatsby v3
• chore(gatsby): update lock file to use npm V7
• chore(gatsby): bump dev version of package

fixes: #451
related: BuilderIO/gatsby-starter-builder#21