fix(indents/yaml): indent sequence/list items

This solves the second issue reported at #1377, in which the cursor
would not be aligned with the line "key2: value2" when entering a new
line below it.

```yaml
- key1: value1
  key2: value2
```

queries/yaml/indents.scm

@@ -1,3 +1,4 @@
 [
   (block_mapping_pair)
+  (block_sequence_item)
 ] @indent