refactor: flow typing (#1012)

* fix: padding

* fix: Minor button alignment issues

* feat: Add icon to invite people button

* WIP

app/components/DropdownMenu/DropdownMenu.js

@@ -31,10 +31,10 @@ class DropdownMenu extends React.Component<Props> {
   @observable left: number;
 
   handleOpen = (
-    openPortal: (SyntheticEvent<*>) => void,
+    openPortal: (SyntheticEvent<>) => void,
     closePortal: () => void
   ) => {
-    return (ev: SyntheticMouseEvent<*>) => {
+    return (ev: SyntheticMouseEvent<HTMLElement>) => {
       ev.preventDefault();
       const currentTarget = ev.currentTarget;
       invariant(document.body, 'why you not here');

app/components/DropdownMenu/DropdownMenuItem.js

@@ -3,7 +3,7 @@ import * as React from 'react';
 import styled from 'styled-components';
 
 type Props = {
-  onClick?: (SyntheticEvent<*>) => *,
+  onClick?: (SyntheticEvent<>) => void | Promise<void>,
   children?: React.Node,
   disabled?: boolean,
 };