OptionalclassA class for the host's own styling.
OptionalsizeWidth and height. A number is CSS pixels; a string is written verbatim, so
'1em' sizes the glyph with the surrounding text. Default: the grid's
native size (24 for tools, 16 for chrome), where the stroke is crispest.
OptionalstrokeStroke width in viewBox units. Default: the tier's *_STROKE.
Options shared by the inline builders.