Columns of views have incorrect datatype

As far as I can tell all columns of views (which don't have any type affinity per default) are coerced to TEXT by datasette-graphql.

One way to figure out the correct datatype would be to inspect all values (or a sample?) and use that information:

```sql
sqlite> select typeof(name), typeof(name_length) from songs_view;
text|integer
text|integer
text|integer
```