plugins: argument of ops should support skipped field

[garyhai]

When change the struct TestArgs of test_plugin/src/lib.rs:

#[derive(Debug, Deserialize)]
struct TestArgs {
  val: String,
  //If the value is not present when deserializing, use the Default::default().
  #[serde(default)]
  skip: String,
}

Run the test according to README then get error report:

error: Uncaught TypeError: Error parsing args: serde_v8 error: ExpectedString
  const result = Deno.core.opSync

It is very useful for optional arguments.

[bartlomieju]

We'll be removing native plugins in the near future #10908 so we won't be adding new features for this API. Respectfully closing.