update: K/N overview and diagrams (#4803)

Author: danil-pavlov

docs/images/native/native-get-started-button.svg

@@ -326,7 +326,7 @@ You can find more information about type mapping in [Interoperability with Swift
 ## Garbage collection and reference counting
 
 Swift and Objective-C use automatic reference counting (ARC). Kotlin/Native has its own [garbage collector](native-memory-manager.md#garbage-collector),
-which is also [integrated with Objective-C/Swift ARC](native-arc-integration.md).
+which is also [integrated with Swift/Objective-C ARC](native-arc-integration.md).
 
 Unused Kotlin objects are automatically removed. You don't need to take additional steps to control the lifetime of
 Kotlin/Native instances from Swift or Objective-C.

docs/images/native/native-objc-kotlin-retain-cycles.png

@@ -249,15 +249,24 @@ cannot be run during the GC pause.
 
 In a _retain cycle_, a number of objects refer each other using strong references cyclically:
 
-![Retain cycles](native-retain-cycle.png){height=200}
+```mermaid
+graph TD
+    A --> B
+    B --> C
+    C --> A
+```
 
 Kotlin's tracing GC and Objective-C's ARC handle retain cycles differently. When objects become unreachable, Kotlin's GC
 can properly reclaim such cycles, while Objective-C's ARC cannot. Therefore, retain cycles of Kotlin objects can be reclaimed,
 while [retain cycles of Swift/Objective-C objects cannot](https://docs.swift.org/swift-book/documentation/the-swift-programming-language/automaticreferencecounting/#Strong-Reference-Cycles-Between-Class-Instances).
 
 Consider the case when a retain cycle contains both Objective-C and Kotlin objects:
 
-![Retain cycles with Objective-C and Kotlin objects](native-objc-kotlin-retain-cycles.png){height=150}
+```mermaid
+graph TD
+    Kotlin.A --> ObjC.B
+    ObjC.B --> Kotlin.A
+```
 
 This involves combining Kotlin's and Objective-C's memory management models that cannot handle (reclaim) retain cycles
 together. That means if at least one Objective-C object is present, the retain cycle of a whole graph of objects

docs/images/native/native-retain-cycle.png

@@ -376,7 +376,7 @@ The application prints "Hello, Kotlin/Native" to the standard output.
 
 ## What's next?
 
-* Complete the [Create an app using C Interop and libcurl](native-app-with-c-and-libcurl.md) tutorial that explains how
+* Complete the [Create an app using C interop and libcurl](native-app-with-c-and-libcurl.md) tutorial that explains how
   to create a native HTTP client and interoperate with C libraries.
 * Learn how to [write Gradle build scripts for real-life Kotlin/Native projects](multiplatform-dsl-reference.md).
 * Read more about the Gradle build system in the [documentation](gradle.md).