update layerRect() to handle inconsistent leading and spaceBefore/spaceAfter paragraph props

[fartinmartin]

Current layerRect() will calculate lineGap based on sourceText.style.leading and multiply by number of lines:

aefunctions/src/index.ts

Lines 300 to 307 in a6a7771

	if (layer.text && xHeight) {
	const { fontSize, leading, autoLeading } = layer.text.sourceText.style;
	const lineGap = autoLeading ? fontSize * 1.2 : leading;
	const textSize = fontSize / 2;
	const numLines = textCount(layer.text.sourceText.value, 'line');
	height = lineGap * (numLines - 1) + textSize;
	topLeft = [left, -textSize];
	}

But, if a text layer has per-character styles applied (via UI, or via expressions from something like style-parser) we'd need to calculate lineGap based on the styles at each line's starting character index value.

This PR introduces a new option consistentLeading that when set to false will calculate as described. (Open to a better option name/API here, haha!)

Additionally, the spaceBefore and spaceAfter paragraph props can affect the height of a given text layer. This PR adds the appropriate height given said paragraph spacing as well.

Here's an example project to check out: aefunctions-layerRect.zip

Note: In this PR, I no longer use textCount() to determine numLines. I found the regexp in this PR to be more consistent/expected—let me know if it breaks an edge case I haven't considered!