Add custom navbar support

- default behaviour is backward compatible: all non-post pages
- optionally enable custom navbar using hugo menu functionality

exampleSite/config.toml

@@ -1,5 +1,5 @@
 # Hugo variables
-# 
+#
 baseurl = "https://example.org/"
 languageCode = "en-us"
 title = "Hugo Bootstrap v4 Blog"
@@ -23,6 +23,14 @@ paginate = 5
   name = "Link 2"
   url = "https://example.org"
 
+# custom navbar menu entry.   See the custom_navbar parameter below for
+# details.
+
+#[[menu.navbar]]
+#  name = "Link 1"
+#  url = "https://example.org"
+
+
 # Theme variables
 #
 [params]
@@ -51,6 +59,15 @@ paginate = 5
   #cookie_consent_info_url = "/cookie-information/"
   #cookie_consent_info_url = "http://cookiesandyou.com"
 
+  # customise the contents of the navbar at the top of the page.  The default
+  # behaviour is to list all static pages not in the posts directory. When the
+  # parameter below is set to true you will have to manually add entries to the
+  # navbar, either by adding the following menu variable to the front matter of
+  # the relevant pages
+  #   menu = "navbar"
+  # or by specifying menu entries in a similar way to the sidebar menu above.
+  #custom_navbar = true
+
   [params.sidebar]
     # Optional about block for sidebar (can be Markdown)
     about = "A simple Hugo theme based on the [Bootstrap v4 blog example](http://v4-alpha.getbootstrap.com/examples/blog/)."