fix: Add access to document TOC on mobile (#2279)

* Add TOC button for mobile

* Undo NewDocumentMenu changes

* Place the toc button in the correct position.

* Pass menu props to menuitem

* Update app/menus/TableOfContentsMenu.js

Co-authored-by: Tom Moor <tom.moor@gmail.com>

* Update app/menus/TableOfContentsMenu.js

Co-authored-by: Tom Moor <tom.moor@gmail.com>

* Use the existing prop type

* Write menu inside actions prop

* Prevent blank webpage behaviour for toc

* Use href instead of level to determine target

* Update app/scenes/Document/components/Header.js

Co-authored-by: Tom Moor <tom.moor@gmail.com>

* Add heading to menu items

* Use existing Heading component

Co-authored-by: Tom Moor <tom.moor@gmail.com>

shared/i18n/locales/en_US/translation.json

@@ -206,6 +206,7 @@
   "Share options": "Share options",
   "Go to document": "Go to document",
   "Revoke link": "Revoke link",
+  "Table of contents": "Table of contents",
   "By {{ author }}": "By {{ author }}",
   "Are you sure you want to make {{ userName }} an admin? Admins can modify team and billing information.": "Are you sure you want to make {{ userName }} an admin? Admins can modify team and billing information.",
   "Are you sure you want to make {{ userName }} a member?": "Are you sure you want to make {{ userName }} a member?",
@@ -337,7 +338,6 @@
   "Move current document": "Move current document",
   "Jump to search": "Jump to search",
   "Jump to home": "Jump to home",
-  "Table of contents": "Table of contents",
   "Toggle navigation": "Toggle navigation",
   "Focus search input": "Focus search input",
   "Open this guide": "Open this guide",