Maybe add navigator.permissions.supports()?

[marcoscaceres]

Can't remember if this was raised previously, but was coding something up and found that I had to wrap the API in a try/catch a little bit annoying when a name of a permission might be potentially unknown.

  let permCheck;
  try {
    permCheck = await navigator.permissions.query({ name: "whatever" });
  } catch (err) {
    return; // not supported
  }

I wonder if we can either change the name in the dictionary to allow a DOMString,

const permCheck = await navigator.permissions.query({ name: "whatever" });
permCheck.state === "unknown"; // or "not-supported"

or adds some kind of "navigator.permissions.supports()" method.

if (!navigator.permissions.supports("whatever")){
    return; // not supported, oh well.  
};
const  permCheck = await navigator.permissions.query({ name: "whatever" });

[marcoscaceres]

Covered by https://w3c.github.io/webappsec-permissions-policy/