There is a CopyToClipboard message that the webview sends.
This means the webview needs to send the copy to clipboard message, while sending the contents to copy within the message.
So within a react file I might have access to the window! <- confirmed
Extension sees the rightclick -> Copy command
Extension tells webview to copy via CopyToClipboard
Webview sees message, sends highlighted text back to extension via CopyToClipboard
Extension receives message, places highlighted section in clipboard.