unchecked chrome.runtime.lastError

https://github.com/MetaMask/extension-port-stream/blob/6e32c73a5c7b66ede01fad9d8dc83e9991eed49f/src/index.ts#L14-L15

```
Unchecked runtime.lastError: Could not establish connection. Receiving end does not exist.
```
needs to be handled in this way per https://stackoverflow.com/a/56787332
```js
chrome.runtime.sendMessage('ping', response => {
if(chrome.runtime.lastError) {
// handle error
} else {
// handle response
}
}
```
looks like firefox also puts the error on the port obj
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/Port

also looks like the error is handled more normally for some promise based apis, but likely not relevant to our usage of port
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/lastError

Start by inspecting src/index.ts at lines 14-15, then compare the port usage with the linked WebExtension runtime.lastError and Port documentation. The issue is done when the connection error is handled so it no longer produces an unchecked runtime.lastError warning.

Written by the indexing model from the issue text.