Add missing playground runnable comments (#3258)

diff --git a/docs/topics/channels.md b/docs/topics/channels.md
index 7f41eae..7cf222c 100644
--- a/docs/topics/channels.md
+++ b/docs/topics/channels.md
@@ -573,6 +573,7 @@
 import kotlinx.coroutines.*
 import kotlinx.coroutines.channels.*
 
+//sampleStart
 fun main() = runBlocking<Unit> {
     val tickerChannel = ticker(delayMillis = 100, initialDelayMillis = 0) // create ticker channel
     var nextElement = withTimeoutOrNull(1) { tickerChannel.receive() }
@@ -596,7 +597,9 @@
 
     tickerChannel.cancel() // indicate that no more elements are needed
 }
+//sampleEnd
 ```
+{kotlin-runnable="true" kotlin-min-compiler-version="1.3"}
 
 > You can get the full code [here](../../kotlinx-coroutines-core/jvm/test/guide/example-channel-10.kt).
 >
diff --git a/docs/topics/exception-handling.md b/docs/topics/exception-handling.md
index 5ee5543..c3e6135 100644
--- a/docs/topics/exception-handling.md
+++ b/docs/topics/exception-handling.md
@@ -28,6 +28,7 @@
 ```kotlin
 import kotlinx.coroutines.*
 
+//sampleStart
 @OptIn(DelicateCoroutinesApi::class)
 fun main() = runBlocking {
     val job = GlobalScope.launch { // root coroutine with launch
@@ -47,7 +48,9 @@
         println("Caught ArithmeticException")
     }
 }
+//sampleEnd
 ```
+{kotlin-runnable="true" kotlin-min-compiler-version="1.3"}
 
 > You can get the full code [here](../../kotlinx-coroutines-core/jvm/test/guide/example-exceptions-01.kt).
 >