fix: Correctly calculate the bounds of hat blocks.

[gonfunko]

The basics

• I validated my changes

The details

Resolves

Fixes gonfunko/scratch-blocks#201

Proposed Changes

This PR updates the calculation of the height of hats on blocks. Previously, the height of a hat was the value that was used for the Y position of points on an SVG curve. However, this is not the actual Y position of e.g. the apex of the curve, but rather the Y position of the control points used to define the Bézier curve, which is different from the actual max Y value of the curve itself; note the position of the lower control points relative to the bottom of the curve in the graphic here: https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Paths#b%C3%A9zier_curves.

Per https://stackoverflow.com/a/5327329, the height of the curve is 3/4 the Y position of the control points, at least in the simple situation we use for hats. As a result, before this change, the bounds of hat blocks were incorrect:

With this change, the bounds are as expected across all three built-in renderers: