basic comment added and added some modifications

Author: rdnasim

example/android/app/build.gradle

@@ -8,7 +8,7 @@ if (localPropertiesFile.exists()) {
 
 def flutterRoot = localProperties.getProperty('flutter.sdk')
 if (flutterRoot == null) {
-    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
+    throw GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
 }
 
 def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
@@ -26,7 +26,7 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion flutter.compileSdkVersion
+    compileSdkVersion 33
     ndkVersion flutter.ndkVersion
 
     compileOptions {

example/lib/main.dart

@@ -175,15 +175,23 @@ class HomePageState extends State<HomePage> {
                             setState(() {
                               isLoading = true;
                             });
-                            final flutterBkash = FlutterBkash();
+                            final flutterBkash = FlutterBkash(
+                                bkashCredentials: const BkashCredentials(
+                                    appKey: "",
+                                    appSecret: "",
+                                    password: "",
+                                    username: "",
+                                    isSandbox: false));
 
                             if (_paymentType == PaymentType.createAgreement) {
                               try {
                                 // remove focus from TextField to hide keyboard
                                 FocusManager.instance.primaryFocus?.unfocus();
                                 final result = await flutterBkash
                                     .createAgreement(context: context);
-                                dev.log(result.toString());
+                                dev.log(
+                                    name: "createAgreement -> ",
+                                    result.toString());
                               } on BkashFailure catch (e, st) {
                                 dev.log(e.message, error: e, stackTrace: st);
                               } catch (e) {
@@ -216,11 +224,13 @@ class HomePageState extends State<HomePage> {
                               try {
                                 final res = await flutterBkash.pay(
                                   context: context,
-                                  amount: double.parse(amount),
-                                  marchentInvoiceNumber: "tranId",
+                                  amount: double.parse(amount), // need it double type
+                                  merchantInvoiceNumber: "tranId",
                                 );
 
-                                dev.log(res.toString());
+                                dev.log(
+                                    name: "withoutAgreement -> ",
+                                    res.toString());
                               } on BkashFailure catch (e, st) {
                                 dev.log(e.message, error: e, stackTrace: st);
                               } catch (e) {
@@ -266,12 +276,12 @@ class HomePageState extends State<HomePage> {
                               // Goto BkashPayment page & pass the params
                               try {
                                 final result =
-                                    await flutterBkash.paywithAgreement(
+                                    await flutterBkash.payWithAgreement(
                                   context: context,
                                   amount: double.parse(amount),
                                   agreementId: agreementId,
                                   marchentInvoiceNumber:
-                                      "marchentInvoiceNumber",
+                                      "merchantInvoiceNumber",
                                 );
 
                                 dev.log(result.toString());

lib/src/flutter_bkash.dart

@@ -72,10 +72,11 @@ class FlutterBkash {
     }
   }
 
+  // pay without agreement
   Future<BkashPaymentResponse> pay({
     required BuildContext context,
     required double amount,
-    required String marchentInvoiceNumber,
+    required String merchantInvoiceNumber,
   }) async {
     await _validateToken();
 
@@ -85,7 +86,7 @@ class FlutterBkash {
         final apiResponse = await _bkashApi.payWithoutAgreement(
           idToken: tokenRes.idToken,
           amount: amount.toString(),
-          marchentInvoiceNumber: marchentInvoiceNumber,
+          marchentInvoiceNumber: merchantInvoiceNumber,
         );
 
         return await apiResponse.fold<Future<BkashPaymentResponse>>(
@@ -147,7 +148,8 @@ class FlutterBkash {
     return paymentResponse;
   }
 
-  Future<BkashPaymentResponse> paywithAgreement({
+  // after agreement - pay with agreement
+  Future<BkashPaymentResponse> payWithAgreement({
     required BuildContext context,
     required double amount,
     required String agreementId,
@@ -224,6 +226,7 @@ class FlutterBkash {
     return paymentResponse;
   }
 
+  // create agreement when first time create to agreement
   Future<BkashAgreementResponse> createAgreement({
     required BuildContext context,
   }) async {