fix: Keyboard accessible context menus (#1768)

- Makes menus fully accessible and keyboard driven
- Currently adds 2.8% to initial bundle size due to the inclusion of Reakit and its dependency, popperjs.
- Converts all menus to functional components
- Remove old custom menu system
- Various layout and flow improvements around the menus

closes #1766

app/components/ContextMenu/index.js

@@ -0,0 +1,77 @@
+// @flow
+import { rgba } from "polished";
+import * as React from "react";
+import { Menu } from "reakit/Menu";
+import styled from "styled-components";
+import { fadeAndScaleIn } from "shared/styles/animations";
+import usePrevious from "hooks/usePrevious";
+
+type Props = {|
+  "aria-label": string,
+  visible?: boolean,
+  animating?: boolean,
+  children: React.Node,
+  onOpen?: () => void,
+  onClose?: () => void,
+|};
+
+export default function ContextMenu({
+  children,
+  onOpen,
+  onClose,
+  ...rest
+}: Props) {
+  const previousVisible = usePrevious(rest.visible);
+
+  React.useEffect(() => {
+    if (rest.visible && !previousVisible) {
+      if (onOpen) {
+        onOpen();
+      }
+    }
+    if (!rest.visible && previousVisible) {
+      if (onClose) {
+        onClose();
+      }
+    }
+  }, [onOpen, onClose, previousVisible, rest.visible]);
+
+  return (
+    <Menu {...rest}>
+      {(props) => (
+        <Position {...props}>
+          <Background>
+            {rest.visible || rest.animating ? children : null}
+          </Background>
+        </Position>
+      )}
+    </Menu>
+  );
+}
+
+const Position = styled.div`
+  position: absolute;
+  z-index: ${(props) => props.theme.depths.menu};
+`;
+
+const Background = styled.div`
+  animation: ${fadeAndScaleIn} 200ms ease;
+  transform-origin: ${(props) => (props.left !== undefined ? "25%" : "75%")} 0;
+  background: ${(props) => rgba(props.theme.menuBackground, 0.95)};
+  border: ${(props) =>
+    props.theme.menuBorder ? `1px solid ${props.theme.menuBorder}` : "none"};
+  border-radius: 2px;
+  padding: 0.5em 0;
+  min-width: 180px;
+  overflow: hidden;
+  overflow-y: auto;
+  max-height: 75vh;
+  max-width: 276px;
+  box-shadow: ${(props) => props.theme.menuShadow};
+  pointer-events: all;
+  font-weight: normal;
+
+  @media print {
+    display: none;
+  }
+`;