fix(text)!: mark name and structure property of type extension …

…item as required (#495)

The spec on simple extensions
[states](https://substrait.io/extensions/#simple-extensions):
```
In the places where these entities are referenced, they will be referenced using a URI + name
reference.
```
And for type:
```
Type  | The name as defined on the type object.
```

However this `name` field is not marked as required on the type object
definition in the schema. This PR marks this field as required to make
sure it
can always be referenced.

---------

Co-authored-by: Weston Pace <[email protected]>

text/simple_extensions_schema.yaml

@@ -10,6 +10,7 @@ properties:
     items:
       type: object
       additionalProperties: false
+      required: [name]
       properties:
         name:
           type: string