fix: Ensure menus are always kept on the screen (#1036)

* ensuring dropdowns fit on the screen

* refactoring

* fix flow types

* no longer fixing the elements which should resolve scrolling issues

* fix menus that should be fixed

* styled-components syntax was wrong

* account for fixed dropdowns when handling overflowing menus

* Update app/components/DropdownMenu/DropdownMenu.js

Co-Authored-By: Tom Moor <tom.moor@gmail.com>

app/components/Sidebar/components/DocumentLink.js

@@ -81,7 +81,7 @@ class DocumentLink extends React.Component<Props> {
               document ? (
                 <Fade>
                   <DocumentMenu
-                    position="left"
+                    position="right"
                     document={document}
                     onOpen={() => (this.menuOpen = true)}
                     onClose={() => (this.menuOpen = false)}