Scatter with extra vertical line

I made a simple chart like this:

{
	"line":{
		"color":"#0097A7",
		"width":2
	},
	"type":"scatter",
	"name":"m",
	"x":[
		"1989-04-14T00:00:00+0200",
		"2003-10-01T00:00:00+0200",
		"2004-10-06T00:00:00+0200"
	],
	"y":[
		4.99,
		3.81,
		3.6
	]
}

Output:

How can I make a vertical line at a specific year, say 1998 (on the X axsis):

I’m not sure if this is possible.