doc: sorting arrays

doc/docs.md

@@ -558,6 +558,24 @@ a[0][1][1] = 2
 println(a) // [[[0, 0], [0, 2], [0, 0]], [[0, 0], [0, 0], [0, 0]]]
 ```
 
+#### Sorting arrays
+
+Sorting arrays of all kinds is very simple and intuitive. Special variables `a` and `b`
+are used when providing a custom sorting condition.
+
+```v
+mut numbers := [1, 3, 2]
+numbers.sort()      // 1, 2, 3
+numbers.sort(a > b) // 3, 2, 1
+```
+
+```v
+struct User { age int  name string }
+mut users := [...]
+users.sort(a.age < b.age)   // sort by User.age int field
+users.sort(a.name > b.name) // reverse sort by User.name string field
+```
+
 ### Maps
 
 ```v