What?

Fix ESLint / Prettier configuration.

Fixes Issue #220

Why?

Apparently there is something called wp-prettier which is a maintained fork of prettier, just to add WP styling. There is a whole thing, if you want to dive deep here are some links:

• Prettier Issue #13107
• wp-prettier

I think some other dependency must have overridden the overriding of prettier by @wordpress/scripts's wp-prettier. But now the package.json explicitly states we are using wp-prettier in place of prettier.