Help: Follow clicked links

This also adds a toolbar and a menu which allow you to
navigate back and forth through history ^)

Applications/Help/History.cpp

@@ -0,0 +1,33 @@
+#include "History.h"
+
+void History::push(const StringView& history_item)
+{
+    m_items.shrink(m_current_history_item + 1);
+    m_items.append(history_item);
+    m_current_history_item++;
+}
+
+String History::current()
+{
+    if (m_current_history_item == -1)
+        return {};
+    return m_items[m_current_history_item];
+}
+
+void History::go_back()
+{
+    ASSERT(can_go_back());
+    m_current_history_item--;
+}
+
+void History::go_forward()
+{
+    ASSERT(can_go_forward());
+    m_current_history_item++;
+}
+
+void History::clear()
+{
+    m_items = {};
+    m_current_history_item = -1;
+}