📝 docs(gitbook): update $te API docs

gitbook/api.md

@@ -168,14 +168,14 @@
 
   Translate the locale of `keypath` with pluralization. Translate in preferentially component locale than global locale. If not specified component locale, translate with global locale. If you will specify String value to `arguments`, translate the locale of value. If you wll specify Array or Object value to `arguments`, you must specify with `arguments` of [$t](#tkeypath-lang-arguments).
 
-### $texist(keypath, [arguments])
+### $te(keypath, [lang])
 
 - **Arguments:**
   - `{String} keypath`
-  - `{Array | Object} [arguments]`
+  - `{String} [lang]`
 
 - **Return:**
-  Whether keypath exists (Boolean)
+  Whether keypath exists, boolean value
 
 - **Usage:**
-  Return whether key path exists in Boolean.
+  Check whether key path exists. In Vue instance, If not specified component locale, check with global locale. If you specified `lang`, check the locale of `lang`.