I am trying to add subject while posting in Teams channel. I Am using MicrosoftTeams.PostMessageToChannelV3() by searching I got to know That I can use and teams will recognize but, It is not working.

MicrosoftTeams.PostMessageToChannelV3(
        "Teams grp id",
        "Channel id",
        {
            content: "< h2 >Subject:- xyz< /h2 >",contentType: "html"
        }
    )