Add docs

docs/.vitepress/config.ts

@@ -89,6 +89,7 @@ export default defineConfig({
             { text: 'Storage', link: '/guide/storage.md' },
             { text: 'Assets', link: '/guide/assets.md' },
             { text: 'Content Script UI', link: '/guide/content-script-ui.md' },
+            { text: 'Localization', link: '/guide/localization.md' },
             { text: 'Multiple Browsers', link: '/guide/multiple-browsers.md' },
             { text: 'Auto-imports', link: '/guide/auto-imports.md' },
             { text: 'Vite', link: '/guide/vite.md' },

docs/guide/localization.md

@@ -0,0 +1,159 @@
+---
+outline: deep
+---
+
+# Localization
+
+WXT includes a util, [`i18n`](/api/wxt/i18n/), that provides a type-safe feature-rich alternative to `browser.i18n.getMessage`.
+
+It is available automatically when you create a messages file under the `locales/` directory, and add a `default_locale` to the manifest:
+
+```
+<srcDir>
+└─ locales/
+   ├─ en.json
+   ├─ es.json5
+   ├─ fr.yml
+   ├─ de.yaml
+   └─ ...
+```
+
+> You can use JSON, JSON5, or YAML formats.
+
+```ts
+// wxt.config.ts
+export default defineConfig({
+  manifest: {
+    default_locale: 'en',
+  },
+});
+```
+
+## Message File Format
+
+```yml
+# Use plain strings
+simpleMessage: Hello world!
+
+# Nest strings in objects
+popup:
+  overview:
+    title: Nested text
+
+# Plural form support
+items:
+  1: 1 item
+  n: $1 items
+# Optionally include a custom string for 0
+cartSize:
+  0: Empty
+  1: 1 item
+  n: $1 items
+
+# Or stick with the standard web extension format (with a message, description, and placeholders)
+manifestMessage:
+  message: $THIS$ is translated
+  description: This is not-translated, helps translators
+  placeholder:
+    this:
+      content: This
+```
+
+:::tip
+`locales/<code>.json` is 100% compatible with the standard web extension localization format (`_locales/<code>/messages.json`). If you have existing messages files, just move them into the `locales/` directory.
+:::
+
+## Usage
+
+`i18n` is auto-imported, but can be manually imported from `wxt/i18n`.
+
+```ts
+import { i18n } from 'wxt/i18n';
+```
+
+### Basic Usage
+
+You can access messages by their name:
+
+```yml
+helloWorld: Hello world!
+```
+
+```ts
+i18n.t('helloWorld'); // "Hello world!"
+```
+
+Nested messages are combined into one string using an `_`.
+
+```yml
+popup:
+  overview:
+    title: Hello world!
+```
+
+```ts
+i18n.t('popup_overview_title'); // "Hello world!"
+```
+
+If a message is in the standard web extension format, don't include a `_message`, even if it's nested.
+
+```yml
+helloWorld:
+  message: Hello world!
+  description: Some description
+popup:
+  overview:
+    title:
+      message: Nested Title
+```
+
+```ts
+i18n.t('helloWorld'); // "Hello world!"
+i18n.t('popup_overview_title'); // "Nested Title"
+```
+
+### Substitutions
+
+To insert a custom string into a translation, pass an array of values as the second parameter of the `i18n.t` function:
+
+```yml
+hello: Hello, $1, my name is $2.
+```
+
+```ts
+i18n.t('hello', ['Aaron', 'Mark']); // "Hello Aaron, my name is Mark."
+```
+
+### Plural Form
+
+When getting the translation for text with a plural form, use the `i18n.tp` function.
+
+```yml
+friends:
+  0: I have no friends.
+  1: I have a friend.
+  n: I have many friends.
+```
+
+```ts
+i18n.tp('friends', 0); // "I have no friends."
+i18n.tp('friends', 1); // "I have one friend."
+i18n.tp('friends', 2); // "I have many friends."
+```
+
+The first number is the `count`. It is what decides which form will be used.
+
+Substitutions are not required. But usually, a plural form will look something like this:
+
+```yml
+items:
+  1: 1 item
+  n: $1 items
+```
+
+```ts
+i18n.tp('items', 0, ['0']); // "0 items"
+i18n.tp('items', 1, ['1']); // "1 item"
+i18n.tp('items', 2, ['2']); // "2 items"
+i18n.tp('items', 3, ['3']); // "3 items"
+```

docs/typedoc.json

@@ -5,7 +5,8 @@
     "../src/browser.ts",
     "../src/sandbox",
     "../src/storage.ts",
-    "../src/testing"
+    "../src/testing",
+    "../src/i18n"
   ],
   "plugin": ["typedoc-plugin-markdown", "typedoc-vitepress-theme"],
   "out": "./api",