Add InvoiceService and initial invoice dashboard widget

resources/js/types/index.d.ts

@@ -277,6 +277,21 @@ export function newInvoice(): Invoice {
     }
 }
 
+export interface SalesStatistics {
+    year: number;
+    totalRevenue: number;
+    paid: number;
+    paidPercent: number;
+    draft: number;
+    draftPercent: number;
+    issued: number;
+    issuedPercent: number;
+    due: number;
+    duePercent: number;
+    reminded: number;
+    remindedPercent: number;
+}
+
 export function newBillingData() {
     return {
         companyName: "",