created extensions mechanism and Breadcrumbs extension

doc/configuration.toml

@@ -62,3 +62,11 @@ lang = "en"
 sitebase = ""
 # The site title. If supplied, this will be included in page metadata and used to formulate the default title.
 sitetitle = ""
+
+[extensions]
+# Full classnames of the extensions to be loaded.
+load = ["dragonglass.extensions.breadcrumbs.BreadcrumbExtension"]
+
+[extensions.BreadcrumbExtension]
+# Configuration data for BreadcrumbExtension.
+var = "value"

doc/metadata-values.txt

@@ -16,6 +16,11 @@ tags
     (Obsidian standard metadata)
     List of tags for this page.  Tags may be defined here or inline in the text.
 
+parent
+    (Breadcrumbs extension)
+    Reference to the parent page of this one. May be an Obsidian link, i.e. "[[pagename|text]]".
+    If this page is considered a "root" of a breadcrumb hierarchy, use the value ".".
+
 template
     The file name of the template to be used to render this page, overriding the default.
 

doc/template-vars.txt

@@ -4,6 +4,12 @@ backlinks:
     A list of pages that link to the page being rendered. Formatted as a list of dicts with
     two elements, "name" and "link", containing the page title and the link to it, respectively.
 
+breadcrumbs:
+    (Breadcrumbs extension)
+    A list of pages forming the "breadcrumbs" from a root point to the page being rendered.
+    Formatted as a list of dicts with two elements, "name" and "link", containing the page title
+    and the link to it, respectively.  The last element always has an empty "link" value.
+
 default_stylesheet:
     The filename of the default stylesheet which is generated by dragonglass and added to the
     generated pages.