Avoid using .textContent

[developit]

Text.data is faster: https://esbench.com/bench/590c9cfe99634800a0347ffc

[danielweck]

Indeed, .textContent is an order of magnitude slower. Apart from the code conflicts, is there anything blocking this PR? This is a pretty straight-forward and safe change, as you are checking n.nodeType === 3 (Text node, which is CharacterData and therefore has the data property).