Add French translation (#196)

* Added french version and title/description from json messages

* Revert back default language to en-US

* Code reviewed with prettier :)

* Updated json to add information field

* Updated json to add information block (missed on previous)

* Reviewed code language

* correction traduction "groupes étoilés" en "groupes favoris"

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Co-authored-by: Andy Trouvé <andy@strekol.eu>

messages/en-US.json

@@ -1,4 +1,12 @@
 {
+  "Homepage": {
+    "title": "Share <strong>Expenses</strong> with <strong>Friends & Family</strong>",
+    "description": "Welcome to your new <strong>Spliit</strong> instance !",
+    "button": {
+      "groups": "Go to groups",
+      "github": "GitHub"
+    }
+  },
   "Header": {
     "groups": "Groups"
   },
@@ -287,7 +295,8 @@
   },
   "Locale": {
     "en-US": "English",
-    "fi": "Suomi"
+    "fi": "Suomi",
+    "fr-FR": "French"
   },
   "Share": {
     "title": "Share",