update README about working with sparse images

README.md

@@ -60,16 +60,28 @@ Well done you did it! The last step is to star this repo :smile
 
 ## Supported ROM image types
 
-| Image Type      | file names                          |  platforms    |
-| --------------- | ----------------------------------- | ---- |
-| boot images     | boot.img, vendor_boot.img           |  all |
-| recovery images | recovery.img, recovery-two-step.img |  all |
-| vbmeta images   | vbmeta.img, vbmeta_system.img etc.  |  all |
-| dtbo images     | dtbo.img                            | linux & mac |
-| sparse images   | system.img, vendor.img, product.img etc. | linux & mac |
+| Image Type      | file names                          |  platforms    | note |
+| --------------- | ----------------------------------- | ----------    | ---- |
+| boot images     | boot.img, vendor_boot.img           |  all          | |
+| recovery images | recovery.img, recovery-two-step.img |  all          | |
+| vbmeta images   | vbmeta.img, vbmeta_system.img etc.  |  all          | |
+| dtbo images     | dtbo.img                            | linux & mac | |
+| sparse images   | system.img, vendor.img, product.img etc. | linux & mac | need **hacking mode**\* |
 
 Please note that the boot.img MUST follows AOSP verified boot flow, either [Boot image signature](https://source.android.com/security/verifiedboot/verified-boot#signature_format) in VBoot 1.0 or [AVB HASH footer](https://android.googlesource.com/platform/external/avb/+/master/README.md#The-VBMeta-struct) (a.k.a. AVB) in VBoot 2.0.
 
+**hacking mode**\*:
+
+Open build.gradle.kts, Line #8, change
+```
+val bHackingMode = false
+```
+to
+```
+val bHackingMode = true
+```
+This will enable c++ modules, which is necessary for working with sparse images.
+
 ## compatible devices
 
 | Device Model                   | Manufacturer | Compatible           | Android Version          | Note |