[security concern] window.postMessage / onmessage should restrict / check origin

[liusong1111]

https://github.com/rebase-network/synapse-extension/blob/af0985a81b5a6d578b3605bb459b4487283ffab4/src/contentScript/inject/injectedScript.ts#L39

window.postMessage(requestMessage, '*');

* means no origin restriction, which may cause leaky information.

https://github.com/rebase-network/synapse-extension/blob/af0985a81b5a6d578b3605bb459b4487283ffab4/src/contentScript/contentScript.ts#L42

Maybe window.location.origin is enough?

https://github.com/rebase-network/synapse-extension/blob/af0985a81b5a6d578b3605bb459b4487283ffab4/src/contentScript/contentScript.ts#L50

onmessage should also check origin?

Refs: https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage

https://owasp.org/www-chapter-london/assets/slides/OWASPLondon_PostMessage_Security_in_Chrome_Extensions.pdf

https://labs.detectify.com/2016/12/08/the-pitfalls-of-postmessage/