docs: add docs for inline structs

docs-md/developer-guide/syntax-reference.md

@@ -281,6 +281,12 @@ statement by using the syntax `STRUCT<FieldName FieldType, ...>`. For
 example, `STRUCT<ID BIGINT, NAME STRING, AGE INT>` defines a struct with
 three fields, with the supplied name and type.
 
+You can create a struct in a query by specifying the names of the columns
+and expressions that construct the values, separated by `,` and wrapped with
+curly braces. For example: `SELECT {name col0, ageInDogYears col1*7} AS dogs FROM animals`
+would create a schema `col0 STRUCT<VARCHAR, INTEGER>` (assuming `col0` was a string and
+`col1` was an integer).
+
 Access the fields of a struct by using the `->` operator. For example,
 `SOME_STRUCT->ID` retrieves the value of the struct's `ID` field. For
 more information, see [Operators](#operators).