Jsx mode is ignored when set via @@jsxConfig

When setting the JSX mode in-source via

```rescript
@@jsxConfig({version: 4, mode: "automatic"})
````

it is currently ignored. This is because the AST is

```
Pexp_constant PConst_string ("automatic",Some "js")
```

but the code is matching for

```ocaml
{pexp_desc = Pexp_constant (Pconst_string (value, None))}
```

This problem exists for both 10.1.x and master.