Migrate off "gatsby-plugin-intl"

[samajammin]

Is your feature request related to a problem? Please describe.

During migration to Gatsby v3 (#2528) we've hit warnings that the gatsby-plugin-intl is not compatible with Gatsby v3.

There's an open issue & PR to address this:
wiziple/gatsby-plugin-intl#172

But it appears the project is no longer maintained:
wiziple/gatsby-plugin-intl#168

Describe the solution you'd like

Given all the custom functionality we've already implemented around internationalization (e.g. see our gatsby-node.js file), I think we could remove the plugin entirely & roll our own solution.

I'm keen to explore a solution similar to what we built for the Eth2 launchpad just using react-intl:
ethereum/staking-launchpad#308
Main win here would be to auto-generate string ids so we could keep the English content right in components for easier readability & DX. One thing we'd need to confirm is if Gatsby can be configured to use the defaultMessage approach to auto-generate those string ids. CRA didn't support this out of the box (see formatjs/formatjs#2151).

Describe alternatives you've considered

Looks like there's a fork of gatsby-plugin-intl with Gatsby v3 support:
https://github.com/theowenyoung/gatsby-plugin-intl

[minimalsm]

Codebase would definitely be a lot less intimidating and easier to navigate for newer contributors if there is something we could do here.

[github-actions]

This issue is stale because it has been open 45 days with no activity.

[minimalsm]

Solved