Initialize auto-resize for [[html]] block iframes via postMessage.
Listens for message events on the window and matches each event's
source against the iframe.html-block-iframe elements within the root.
When a valid resize message is received from a matching iframe, the
iframe's height is updated.
Parameters
root: HTMLElement
The root DOM element containing rendered Wikidot markup.
Initialize auto-resize for
[[html]]block iframes viapostMessage.Listens for
messageevents on thewindowand matches each event'ssourceagainst theiframe.html-block-iframeelements within the root. When a valid resize message is received from a matching iframe, the iframe's height is updated.