build: switch from yarn to npm to manage js dependencies and move js contents to root

yarn v1 is being deprecated and starts to have some issues

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

src/i18n/langs.json

@@ -0,0 +1,30 @@
+{
+  "ar": "العربية",
+  "bn": "বাংলা",
+  "ca": "Català",
+  "cs": "čeština",
+  "cy": "Cymraeg",
+  "de": "Deutsch",
+  "en": "English",
+  "es": "Español",
+  "fa": "فارسی",
+  "fi": "suomi",
+  "fr": "Français",
+  "gd": "Gàidhlig",
+  "gl": "Galego",
+  "hr": "Hrvatski",
+  "hu": "Magyar",
+  "id": "Bahasa Indonesia",
+  "it": "Italiano",
+  "ja": "日本語",
+  "nl": "Nederlands",
+  "nn": "Nynorsk",
+  "oc": "Occitan",
+  "pl": "Polski",
+  "pt_BR": "Português brasileiro",
+  "ru": "Русский",
+  "sl": "Slovenščina",
+  "sv": "Svenska",
+  "zh_Hans": "简体字",
+  "zh_Hant": "繁體字"
+}