chore(examples): update Introduction examples

Author: AlexanderPrendota

examples/01_introduction/00_description.md

@@ -0,0 +1,25 @@
+# Equality Checks
+
+Kotlin uses `==` for structural comparison and `===` for referential comparison.
+
+More precisely, `a == b` compiles down to `a == null ? b == null : a.equals(b)`.
+
+<div class="language-kotlin" theme="idea">
+
+```kotlin
+fun main() {
+//sampleStart
+
+  val authors = setOf("Shakespeare", "Hemingway", "Twain")
+  val writers = setOf("Twain", "Shakespeare", "Hemingway")
+
+  println(authors == writers)   // 1
+  println(authors === writers)  // 2
+//sampleEnd
+}
+```
+
+</div>
+
+1. Returns `true` because it calls `authors.equals(writers)` and sets ignore element order.
+2. Returns `false` because `authors` and `writers` are distinct references.