Add information about new displayName property for languages

Related to: aseprite/aseprite#3964

Author: dacap

extensions/languages.md

@@ -1,35 +1,44 @@
 # Languages
 
-Content a `.aseprite-extension` file for a language extension:
+This is an example of a possible extension to translate Aseprite to
+Spanish. The content a `.aseprite-extension` file for a language
+extension can be something like this:
 
 ```
-language-example.aseprite-extension
+spanish-language.aseprite-extension
 |
 +-- package.json
-|
-+-- my-language.ini
++-- es.ini
 ```
 
-Content of `package.json`:
+Content of `package.json`, e.g.:
 
 ```
 {
-  "name": "language-example",
-  "displayName": "Language Example",
-  "description": "Translation to Language Example by Full Name",
+  "name": "spanish-language",
+  "displayName": "Spanish Translation",
+  "description": "Translation to Spanish Example by Full Name",
   "version": "1.0",
   "author": { "name": "Full Name", "url": "https://twitter.com/your_username_or_homepage_url" },
   "categories": [
     "Languages"
   ],
   "contributes": {
     "languages": [
-      { "id": "my-language", "path": "./my-language.ini" }
+      { "id": "es",
+        "path": "./es.ini",
+        "displayName": "Español" }
     ]
   }
 }
 ```
 
+The `contributes.languages.displayName` property was introduced in
+**Aseprite v1.3-rc5** to show the language instead of the language code/ID
+(e.g. `es`) in the *Edit > Preferences > General > Language* combobox.
+
+For the `contributes.languages.id` use an [ISO 639-1 language code](https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes).
+
 ---
 
 **SEE ALSO**