CSS and markdown, in a single file

[aborruso]

Hi,
I'm writing this gantt in a markdown file

gantt
    title SVC S1-01
    weekday monday
    dateFormat YYYY-MM-DD
    axisFormat %b %d
    todayMarker off
    tickInterval 2day
    section OU-S1-01-01
        GSP sample production    : 2022-09-02, 2022-09-07
        GSP sample validation    : 2022-09-02, 2022-09-13
        GSP sample delivery to PC : milestone, m2, 2022-09-22, 0d
        Exploitation tool release : milestone, m2, 2022-10-02, 0d
    section OU-S1-01-02
        GSP sample production    : 2022-09-06, 2022-09-13
        GSP sample validation    : 2022-09-06, 2022-09-22
        GSP sample delivery to PC : milestone, m2, 2022-09-29, 0d
        Exploitation tool release : milestone, m2, 2022-10-06, 0d

Is there a way to apply a CSS using only a single markdown file?

As this one

.grid .tick {
  stroke: lightgrey;
  opacity: 0.3;
  shape-rendering: crispEdges;
}

Thank you