No way to get to next line when doing ```[language] shortcut for codeblocks

[RobertBrunhage]

• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• I have read the documentation and cannot find an answer.

Describe the bug
Testing in https://mdxeditor.dev/editor/demo go to the bottom of the page and write ```js followed by space. Now try to get to the next line to write in. (I would expect this to work with shift+enter or just clicking below it).

When using the code block button in the navbar it will add a newline below the codeblock to continue writing in.

Reproduction
Testing in https://mdxeditor.dev/editor/demo go to the bottom of the page and write ```js followed by space

To Reproduce
Steps to reproduce the behavior:

1. https://mdxeditor.dev/editor/demo
2. Click on the last editable part of the markdown editor
3. write ```js followed by enter
4. try to write after the codeblock

Expected behavior
Should be able to continue after writing a codeblock

Desktop (please complete the following information):

• OS: MacOs
• Chrome

[petyosi]

That's a legit problem. I have a code that might need some tweaking, as I believe that down arrow should be able to exit the code block, even if it means creating a new paragraph. Right now, you have to press twice if the block is empty.

@RobertBrunhage if you're interested, I'm happy to accept an improvement PR - this is the code block that does some special handling of the codemirror blocks.

editor/src/plugins/sandpack/useCodeMirrorRef.ts

Lines 28 to 56 in a87df2f

	const onKeyDownHandler = React.useCallback(
	(e: KeyboardEvent) => {
	if (e.key === 'ArrowDown') {
	const state = codeMirrorRef?.current?.getCodemirror()?.state
	if (state) {
	const docLength = state.doc.length
	const selectionEnd = state.selection.ranges[0].to
	if (docLength === selectionEnd) {
	// escaping once
	if (!atBottom.current) {
	atBottom.current = true
	} else {
	// escaping twice
	activeEditor?.update(() => {
	const node = $getNodeByKey(nodeKey)!
	const nextSibling = node.getNextSibling()
	if (nextSibling) {
	codeMirrorRef?.current?.getCodemirror()?.contentDOM.blur()
	node.selectNext()
	} else {
	node.insertAfter($createParagraphNode())
	}
	})
	atBottom.current = false
	}
	}
	}
	} else if (e.key === 'ArrowUp') {