function isCoalesceExpression(node) {
	return node.type === "LogicalExpression" && node.operator === "??";
}
Check if the given node is a nullish coalescing expression or not.

The three binary expressions logical-or (`||`), logical-and (`&&`), and
coalesce (`??`) are known as `ShortCircuitExpression`.
But ESTree represents those by `LogicalExpression` node.

This function finds only coalesce expressions of `LogicalExpression` node.
@param {ASTNode} node The node to check.
@returns {boolean} `true` if the node is `??`.