feat: add examples with descriptions

exl/01_conditions.fzs

@@ -0,0 +1,30 @@
+// When you need to check some value
+//  a conditional statements might help you
+
+int valueToCheck = 2 + 2;
+if (valueToCheck == 4)
+{
+  printline("Yay! 2 + 2 = 4");
+}
+
+// Conditional statement uses condition in pairs
+//  after `if` keyword and executes command(s) after
+//  if condition turns out to be true
+
+// Otherwise, to execute block when condition turns
+//  out to be false, you can use `else` keyword:
+
+int age = 30;
+
+if (age <= 20)
+  printline("You're too young");
+else
+{
+  age = 20;
+  printline("You looks too young!");
+}
+
+// NOTE: If you need to execute only one statement
+//  inside `if` or `else` block, then the curly
+//  braces can be omitted.
+