docs: update README structure

Author: Fl0rk

README.md

@@ -10,15 +10,18 @@ To understand how the library blocks screen capture, inspect the compiled Mach-O
 
 By looking at related iOS system APIs, we can identify three defense layers used by the library:
 
-1. **The Visual Layer (`UITextField`):** The library uses the common `setSecureTextEntry:` trick to hide the app UI during screenshots or screen recording.
+### 1. Visual Layer (`UITextField`)
+The library uses the common `setSecureTextEntry:` trick to hide the app UI during screenshots or screen recording.
 
 ![image1](img/img1.png)
 
-2. **The Active Check Layer (`UIScreen`):** The `screenIsRecording()` function checks `[UIScreen mainScreen].isCaptured` directly to detect whether the screen is being recorded.
+### 2. Active Check Layer (`UIScreen`)
+The `screenIsRecording()` function checks `[UIScreen mainScreen].isCaptured` directly to detect whether the screen is being recorded.
 
 ![image2](img/img2.png)
 
-3. **The Event Detection Layer (`NSNotificationCenter`):** The `screenshotObserver(using:)` and `screenRecordObserver(using:)` functions show that the library listens for screenshot and screen recording notifications through `NSNotificationCenter` and forwards them to the Flutter layer.
+### 3. Event Detection Layer (`NSNotificationCenter`)
+The `screenshotObserver(using:)` and `screenRecordObserver(using:)` functions show that the library listens for screenshot and screen recording notifications through `NSNotificationCenter` and forwards them to the Flutter layer.
 
 ![image3](img/img3.png)