explicit preview request/response;
commands, icons, menus like VSCode markdown preview;
clarified Uri information (again);
tuned;
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd" [
<!ENTITY ns_flows "http://ns.adobe.com/Flows/1.0/">
]><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16"><polygon fill="#656565" points="10,2 7.414,2 8.414,3 9,3 9,3.586 9,4 9,4.414 9,6 12,6 12,13 4,13 4,8 3,8 3,14 13,14 13,5"/><polygon fill="#00539C" points="5,1 3,1 5,3 1,3 1,5 5,5 3,7 5,7 8,4"/></svg>
