builtin: add string.split_by_whitespace()

vlib/builtin/string_test.v

@@ -902,3 +902,10 @@ fn test_sorter() {
 	assert arr[2].s == 'ccc'
 	assert arr[2].i == 102
 }
+
+fn test_split_by_whitespace() {
+	assert 'a bcde'.split_by_whitespace() == ['a', 'bcde']
+	assert '  sss \t  ssss '.split_by_whitespace() == ['sss', 'ssss']
+	assert '\n xyz \t abc   def'.split_by_whitespace() == ['xyz', 'abc', 'def']
+	assert ''.split_by_whitespace() == []
+}