I added a decoration and set before to my vscode extension.

const decoration: vscode.DecorationOptions = {
        range: new vscode.Range(startPos.line, startPos.character, endPos.line, endPos.character),
        hoverMessage,
        renderOptions: {
            before: {
                contentIconPath: vscode.Uri.parse(decorationBase64Result.base64),
                height: vscode.workspace.getConfiguration('editor').get('fontSize')
            },
        },
};

And I want to add hoverMessage to this before, but I found the doc only has the hoverMessage to decoration itself.

I want to set the hoverMessage for the before but not the code in range, like Gitlens. How can I do this?