Feat: locale for date and button for adding next month

src/store/travail/index.js

@@ -34,6 +34,10 @@ const travail = {
             // Get all the months
             return Object.keys(state.months).sort().reverse()
         },
+        lastMonthDate(state) {
+            // Return the date of the last registered month
+            return Object.keys(state.months).sort().reverse()[0]
+        },
         months: (state, getters) => {
             // Get in range months
             const a = Object.keys(state.months)