chore(examples): add Control structures examples

Author: AlexanderPrendota

examples/02_advanced/00_description.md

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+# Control structures

examples/02_advanced/01_namedArguments.md

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+# When
+
+Kotlin do not have `switch` statement, instead of it it has more smart and clear `when` contrusction. Let's take a look
+
+<div class="language-kotlin" theme="idea">
+```kotlin
+fun main() {
+    cases("Hello")
+    cases(1)
+    cases(0L)
+    cases(MyClass())
+    cases("hello")
+}
+
+fun cases(obj: Any) {
+    when (obj) {
+        1 -> println("One")                          // 1
+        "Hello" -> println("Greeting")               // 2
+        is Long -> println("Long")                   // 3
+        !is String -> println("Not a string")        // 4
+        else -> println("Unknown")                   // 5
+    }
+}
+
+class MyClass() {
+}
+```
+</div>
+
+
+1. Check whether `obj` equals to `1`
+2. Check for string
+3. Or even instance check
+4. Negative instance check
+5. Default statement (might be omitted)

examples/02_advanced/02_extensionFunctions.md

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+#Loops
+
+### for, while, do-while
+
+<div class="language-kotlin" theme="idea">
+
+```kotlin
+fun main() {
+//sampleStart
+    val cakes = listOf("carrot", "cheese", "chocolate")
+    
+    for (cake in cakes) {                               // 1
+        println("Yummy, it's a $cake cake!")
+    }
+
+//sampleEnd
+}
+```
+
+</div>
+
+1. Loops through each cake in the list
+
+<div class="language-kotlin" theme="idea">
+
+```kotlin
+//sampleStart
+fun eatACake() = println("Eat a Cake")
+fun bakeACake() = println("Bake a Cake")
+
+fun main() {
+    var cakesEaten = 0
+    var cakesBaked = 0
+    
+    while (cakesEaten < 5) {                    // 1
+        eatACake()
+        cakesEaten ++
+    }
+    
+    do {                                        // 2
+        bakeACake()
+        cakesBaked++
+    } while (cakesBaked < cakesEaten)
+
+}
+//sampleEnd
+```
+
+</div>
+
+While and do-while constructs work similarly to most languages.
+
+1. Performs the block while the condition is false
+2. Performs the block first, and then loops while evaluating the while condition.
+
+### Iterators
+
+<div class="language-kotlin" theme="idea">
+
+```kotlin
+class Animal(val name: String)
+
+class Zoo(val animals: List<Animal>) {
+
+    operator fun iterator(): Iterator<Animal> {             // 1
+        return animals.iterator()                           // 2
+    }
+}
+
+fun main() {
+
+    val zoo = Zoo(listOf(Animal("zebra"), Animal("lion")))
+
+    for (animal in zoo) {                                   // 3
+        println("Watch out, it's a ${animal.name}")
+    }
+
+}
+```
+
+</div>
+
+1. Providing an iterator implementation (marked with operator modifier).
+2. Returns the iterator for the list, which meets the method requirements
+    1. next(): Animal
+    2. hasNext(): Boolean
+3. Loops through each animal in the zoo
+
+The iterator can be declared on the type or as an extension function.

examples/02_advanced/03_Data classes.md

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+# Ranges
+
+<div class="language-kotlin" theme="idea">
+
+```kotlin
+fun main() {
+//sampleStart
+    for(i in 0..3) {             // 1
+        print(i)
+    }
+    print(" ")
+
+    for(i in 2..8 step 2) {      // 2
+        print(i)
+    }
+    print(" ")
+
+    for (c in 'a'..'d') {        // 3
+        print(c)
+    }
+    print(" ")
+
+    for (c in 'a'..'g' step 2) { // 4
+        print(c)
+    }
+    print(" ")
+
+    for (i in 3 downTo 0) {      // 5
+        print(i)
+    }
+    print(" ")
+
+    val x = 2
+    if (x in 1..10) {            // 6
+        print(x)
+    }
+    print(" ")
+
+    val y = 3
+    if (y !in 1..4) {            // 7
+        print(y)
+    }
+//sampleEnd
+}
+```
+
+</div>
+
+1. Create range starting from 0 up to 3 (inclusive) and iterate over it
+2. You can define increment step for consecutive elements
+3. Char ranges can be created as well
+4. Increment step for char ranges are also valid
+5. To create a range in _reverse_ order use `downTo()` function
+6. Ranges are also useful in `if` statements
+7. `!in` is oposite of `in`. Statement is equal to `_false_`
+