Add endpoint for Company model

lib/inventree/company.dart

@@ -0,0 +1,20 @@
+import 'model.dart';
+
+
+class InvenTreeCompany extends InvenTreeModel {
+  @override
+  String URL = "company/";
+
+  InvenTreeCompany() : super();
+
+  InvenTreeCompany.fromJson(Map<String, dynamic> json) : super.fromJson(json) {
+    // TODO
+  }
+
+  @override
+  InvenTreeModel createFromJson(Map<String, dynamic> json) {
+    var company = InvenTreeCompany.fromJson(json);
+
+    return company;
+  }
+}