Target current tab from any iframe

[fregante]

We have tabId: "this" for this purpose:

• New named targets solution + add some notes/docs #53

however it only works between extension pages because:

• only extension pages can use chrome.tab without intermediary steps

• the current logic only handles "this" by comparing the sender to the current context, but this could be trivially changed:

   on send:
   	if isContentScript && tabId === "this"
   		send to background
  
   on background receive:
   	if tabId === "this"
   		forward to this.trace[0].tab.id

  webext-messenger/source/thisTarget.ts

  Lines 68 to 71 in ed302a0

  	// Set "this" tab to the current tabId
  	if (to.tabId === "this" && thisTarget.tabId === from.tab?.id) {
  	to.tabId = thisTarget.tabId;
  	}

[fregante]

This is no longer used/necessary after the migration to sidePanel, but it can be added in these two places if it ever becomes useful again.

webext-messenger/source/receiver.ts

Lines 61 to 63 in 3ac32d7

	if (action === "forward") {
	log.debug(type, seq, "🔀 forwarded", { sender, target });
	handleMessage = async () => messenger(type, meta, target, ...args);

webext-messenger/source/sender.ts

Lines 299 to 300 in 3ac32d7

	"↗️ sending message to tab",
	tabId,