add kotlin-playground styles to CONCURRENCY.md (#2071)

CONCURRENCY.md

@@ -23,6 +23,9 @@
   Once a worker is started with the `Worker.start` function call, it can be addressed with its own unique integer
  worker id. Other workers, or non-worker concurrency primitives, such as OS threads, can send a message
  to the worker with the `execute` call.
+ 
+<div class="sample" markdown="1" theme="idea" data-highlight-only>
+  
  ```kotlin
    val future = execute(TransferMode.SAFE, { SomeDataForWorker() }) {
        // data returned by the second function argument comes to the
@@ -39,6 +42,9 @@
       result -> println("result is $result")
    }
 ```
+
+</div>
+
  The call to `execute` uses a function passed as its second parameter to produce an object subgraph
  (i.e. set of mutually referring objects) which is then passed as a whole to that worker, it is then no longer
  available to the thread that initiated the request. This property is checked if the first parameter
@@ -92,7 +98,10 @@
  mentioned above it is possible to build popular data structures, like concurrent hashmap or shared cache with
  Kotlin/Native. It is possible to rely upon shared C data, and store in it references to detached object subgraphs.
  Consider the following .def file:
-```
+ 
+<div class="sample" markdown="1" theme="idea" mode="c">
+
+```c
 package = global
 
 ---
@@ -103,14 +112,23 @@ typedef struct {
 
 SharedData sharedData;
 ```
+
+</div>
+
 After running the cinterop tool it can share Kotlin data in a versionized global structure,
 and interact with it from Kotlin transparently via autogenerated Kotlin like this:
+
+<div class="sample" markdown="1" theme="idea" data-highlight-only>
+
 ```kotlin
 class SharedData(rawPtr: NativePtr) : CStructVar(rawPtr) {
     var version: Int
     var kotlinObject: COpaquePointer?
 }
 ```
+
+</div>
+
 So in combination with the top level variable declared above, it can allow looking at the same memory from different
 threads and building traditional concurrent structures with platform-specific synchronization primitives.