Foramontano/adding languages (#89)

- Doc that describes the steps to add a new language  to Spacedeck Open
- New file with translated entries for using in Spacedeck Open in Spanish
- Include 'es' as new locale in Spacedeck Open
- Include a radiobutton for users could select the new language

docs/adding_languages.md

@@ -0,0 +1,26 @@
+## Adding a new language to Spacedeck Open
+
+To add a new language to Spacedeck Open, follow these steps:
+
+*The steps are ilustrated with Spanish (locale 'es') as the new language*
+
+- Include the new locale ('es') at the locale list (./spacedeck.js)
+```
+    locales: ["en",..., "es"],
+```
+- Create the new translation file (/locales/**es.js** thar it's a copy of /locales/en.js). and translate the entries.
+- Include the javascript for letting Spanish info accesible (at the end of /views/spacedeck.html)
+
+  ```
+    ...
+    window.locales.es = {};
+    ...
+    window.locales.es.translation = {% include "./../locales/es.js" %};
+  </script>
+  ```
+- Include a radiobutton for users could seleect the new language (/views/partials/account.html)
+  ```
+    <label class="radio" v-bind:class="{checked: user.prefs_language=='es'}" v-on:click="save_user_language('es')">
+      <input type="radio" id="user-preferences_language" name="language" value="es"><span>Español</span>
+    </label>
+  ```