chore(api): document window.__TAURI__ option and allowlist (tauri-apps#223)

Author: lucasfernog

docs/en/api/js/index.md

@@ -7,6 +7,12 @@ hide_title: true
 
 # @tauri-apps/api
 
+The `@tauri-apps/api` package is a JavaScript interface to the Tauri API.
+It is written in TypeScript and allows you to call core APIs and your own commands.
+Note that some APIs must be enabled under `tauri.conf.json > tauri > allowlist`, and each module explains the configuration.
+
+If you are not using a module bundler, you can use this API as a `window.__TAURI__` object by enabling it on `tauri.conf.json > build > withGlobalTauri`.
+
 ## Table of contents
 
 ### Modules

docs/en/usage/guides/command.md

@@ -35,7 +35,7 @@ Now, you can invoke the command from your JS code:
 ```js
 // With the Tauri API npm package:
 import { invoke } from '@tauri-apps/api/tauri'
-// With the Tauri global script:
+// With the Tauri global script, enabled when `tauri.conf.json > build > withGlobalTauri` is set to true:
 const invoke = window.__TAURI__.invoke
 
 // Invoke the command