toSizingValue = (/** @type {string} */ declarationName, /** @type {string} */ declarationValue) => (
	declarationName in sizeProps && typeof declarationValue === 'string'
		? declarationValue.replace(
			/^((?:[^]*[^\w-])?)(fit-content|stretch)((?:[^\w-][^]*)?)$/,
			(data, lead, main, tail) => (
				lead + (
					main === 'stretch'
						? `-moz-available${tail};${toHyphenCase(declarationName)}:${lead}-webkit-fill-available`
					: `-moz-fit-content${tail};${toHyphenCase(declarationName)}:${lead}fit-content`
				) + tail
			),
		)
	: String(declarationValue)
)
Returns a declaration sizing value with polyfilled sizing keywords.