Try load proto files with import assertions when feature lands

from
```js
const path = new URL("./svc.proto", import.meta.url);
const text = await Deno.readTextFile(protoPath);
```

to

```js
import text from "./svc.proto" assert { type: "text" };
```
or even
```js
import proto from "./svc.proto" assert { type: "proto" };
```