BREAKING CHANGE(core): Rebrand XInvoice to EInvoice: update package name, class names, imports, and documentation

ts/interfaces.ts

@@ -1,4 +1,4 @@
-export interface IXInvoice {
+export interface IEInvoice {
   InvoiceNumber: string;
   DateIssued: string; // Date in ISO 8601 format
   Seller: IParty;
@@ -81,9 +81,9 @@ export interface ValidationResult {
 }
 
 /**
- * Options for the XInvoice class
+ * Options for the EInvoice class
  */
-export interface XInvoiceOptions {
+export interface EInvoiceOptions {
   validateOnLoad?: boolean; // Whether to validate when loading an invoice
   validationLevel?: ValidationLevel; // Level of validation to perform
 }