Context menu with some commands (#217)

src/components/Popover.tsx

@@ -0,0 +1,24 @@
+import React from "react";
+
+type Props = {
+  top?: number;
+  left?: number;
+  children?: React.ReactNode;
+  onCloseRequest?(): void;
+};
+
+export function Popover({ children, left, onCloseRequest, top }: Props) {
+  return (
+    <div className="popover" style={{ top: top, left: left }}>
+      <div
+        className="cover"
+        onClick={onCloseRequest}
+        onContextMenu={e => {
+          e.preventDefault();
+          if (onCloseRequest) onCloseRequest();
+        }}
+      />
+      {children}
+    </div>
+  );
+}