Fix inconsistent rendering of block mathematical expressions

[yp05327]

Fix #28735

GitHub render \```math\``` as a block now.
Add display class will render it as a block.

After:

[silverwind]

Where is this display class from? I would recommend using tailwind, e.g. tw-block for display: block, ref.

[yp05327]

gitea/web_src/js/markup/math.js

Lines 32 to 46 in 0c273f1

	const displayMode = el.classList.contains('display');
	const nodeName = displayMode ? 'p' : 'span';
	try {
	const tempEl = document.createElement(nodeName);
	katex.render(source, tempEl, {
	maxSize: MAX_SIZE,
	maxExpand: MAX_EXPAND,
	displayMode,
	});
	target.replaceWith(tempEl);
	} catch (error) {
	displayError(target, error);
	}
	}

It is used for select the display mode in js. It doesn't look like a class for css.

[silverwind]

Ah I see, the JS is then turning it into katex-display in the output which does the block rendering.

I also tested this with inline math and can confirm it does not regress them.

[silverwind]

Refactor for the future: Turn display class into data-is-display="true" for clarity.