function Deno.copyFile
copyFile(fromPath: string | URL,toPath: string | URL,): Promise<void>
Copies the contents and permissions of one file to another specified path,
by default creating a new file if needed, else overwriting. Fails if target
path is a directory or is unwritable.
```ts
await Deno.copyFile("from.txt", "to.txt");
```
Requires `allow-read` permission on `fromPath`.
Requires `allow-write` permission on `toPath`.
Promise<void>