[feat]: update i18n contribution docs (#2440)

CONTRIBUTING.md

@@ -169,6 +169,10 @@ Once that has completed, run `xcode-select --install` in the terminal to install
 
 Also ensure that Rosetta is installed, as a few of our dependencies require it. You can install Rosetta with `softwareupdate --install-rosetta --agree-to-license`.
 
+### Translations
+Check out the [i18n README](interface/locales/README.md) for more information on how to contribute to translations.
+
+
 ### Credits
 
 This CONTRIBUTING.md file was inspired by the [github/docs CONTRIBUTING.md](https://github.com/github/docs/blob/main/CONTRIBUTING.md) file, and we extend our gratitude to the original author.

interface/locales/README.md

@@ -1,3 +1,24 @@
+
+# Locales
+
+This directory contains the translations for the application.
+
+## Adding a new language
+
+To add a new language, create a new directory with the language code (e.g. `es` for Spanish) and copy the `en` directory into it. Then, translate the strings in the new directory.
+
+To display the new language as an option in the application, add the language code to the `LANGUAGE_OPTIONS` array in `interface/app/$libraryId/settings/client/appearance.tsx`.
+
+```ts
+export const LANGUAGE_OPTIONS = [
+  { value: 'en', label: 'English' },
+  { value: 'es', label: 'Español' },
+  // The rest of the languages
+];
+```
+
+## Syncing locales
+
 This command will help you sync locales with the source language (en) and find missing keys.
 
 `npx i18next-locales-sync -p en -s it -l ./interface/locales`