chore: Migrate prettierrc.json to typed prettier.config.mjs file

[radmorecameron]

Summary | Résumé

1-3 sentence description of the changed you're proposing, including a link to a GitHub Issue # or Trello card if applicable.

Change prettierrc.json to typed prettier.config.mjs file

---

Description en 1 à 3 phrases de la modification proposée, avec un lien vers le

This PR changes prettierrc.json to a prettier.config.mjs file, This gives us proper type support and autocomplete. jsxBracketSameLine was removed from the config as well since it is deprecated and says to "use bracketSameLine instead"

Test instructions | Instructions pour tester la modification

• edit a value in prettier.config.js, notice that it now has autocomplete