closes https://github.com/TryGhost/Team/issues/3307
This commit includes several important updates to add internationalisation (i18n) support within the signup form package:
- Modified the translate script in `package.json` to include translations for the signup form.
- Added a new test for the signup form resources in `i18n.test.js`.
- Updated `tsconfig.json` to allow synthetic default imports.
- Made updates to `package.json`, including adding a prebuild command for `@tryghost/i18n` to ensure typescript declaration files get built.
- added `vite-plugin-commonjs` so we can bundle commonjs packages to be useable by the browser.
- In `App.tsx`, imported the `i18n` library and created an `i18n` instance for the `signup-form` namespace. This `i18n` instance's `t` function was added to the application context.
- Updated the `AppContextType` in `AppContext.ts` to include the `t` function from i18n
Co-authored-by: Daniel Lockyer <hi@daniellockyer.com>
