Wysiwyg: preserves line feeds in code block mode

[bourdaisj]

Fix #3200

[ssddanbrown]

Thank you once again @Julesdevops!

This change was definitely an improvement to preserve the newlines.
Unfortunately it alone would not fully address the issue in #3200.

When the selection spanned across multiple top-level nodes, inserting a code block would attempt to (and breakingly) convert the whole page into a code block. You would also see all text within the code content editor popup. This was due to my usages of getNode() within the below lines:

BookStack/resources/js/components/wysiwyg-editor.js

Lines 139 to 148 in 815f8d7

	const providedCode = editor.selection.getNode().textContent;
	window.components.first('code-editor').open(providedCode, '', (code, lang) => {
	const wrap = document.createElement('div');
	wrap.innerHTML = `<pre><code class="language-${lang}"></code></pre>`;
	wrap.querySelector('code').innerText = code;
	editor.formatter.toggle('pre');
	const node = editor.selection.getNode();
	editor.dom.setHTML(node, wrap.querySelector('pre').innerHTML);
	editor.fire('SetContent');

When multiple top-level nodes are selected this would resolve to the shared parent body, hence we would fetch all text from those and attempt to replace the whole body with code on code-block-save.

I found a handy editor.selection.getContent({format: 'text'}) method which is smart and provides just the selection, even if terminating part-way through a block.

I followed up your changes with b2f863e which uses this method and simplifies the strange stuff I was doing to set the code block, to make the selection replacement more accurate.

[bourdaisj]

Indeed a far better solution! thanks for following up on this