Add a download link to each page, next to the "Edit on GitHub" link.

docs/_config.yml

@@ -110,6 +110,18 @@ gh_edit_branch: "main" # the branch that your docs is served from
 gh_edit_source: docs # the source that your files originate from
 gh_edit_view_mode: "tree" # "tree" or "edit" if you want the user to jump into the editor immediately
 
+# Footer "Download offline copy" link -- points at the offline-site
+# zip attached to the latest GitHub release (cut by the manual
+# `workflow_dispatch` path in .github/workflows/jekyll-gh-pages.yml).
+# Rendered inside the same flex row as the "Edit this page" link,
+# with id="download-offline" on the <a>. Emitted in both the online
+# _site/ and the offline _site-offline/ trees -- online readers use
+# it to fetch the offline copy, offline readers use it to refresh
+# theirs against the latest release.
+gh_offline_link: true
+gh_offline_link_text: "Download offline copy"
+gh_offline_link_url: "https://github.com/twinbasic/documentation/releases/latest/download/twinbasic-docs-offline.zip"
+
 # When true, the Offlinify plugin (_plugins/offlinify.rb) runs at the
 # end of the build, copies _site/ to _site-offline/, rewrites every
 # URL to a page-relative form, patches a couple of just-the-docs JS

docs/_includes/components/footer.html

@@ -0,0 +1,49 @@
+{%- comment -%}
+  Shadow of just-the-docs's _includes/components/footer.html, kept in
+  sync with the upstream 0.10.x layout. The only addition is the
+  "Download offline copy" <p> rendered inside the same flex row as
+  "Edit this page on GitHub", gated on `site.gh_offline_link` (set in
+  _config.yml). The link's <a> carries id="download-offline" as a
+  stable hook, mirroring id="edit-this-page" next to it. Both the
+  online and offline trees render the link -- online users use it to
+  fetch the offline copy, offline users use it to refresh theirs.
+{%- endcomment -%}
+{% capture footer_custom %}
+  {%- include footer_custom.html -%}
+{% endcapture %}
+{% if footer_custom != "" or site.last_edit_timestamp or site.gh_edit_link or site.gh_offline_link or site.back_to_top %}
+  <hr>
+  <footer>
+    {% if site.back_to_top %}
+      <p><a href="#top" id="back-to-top">{{ site.back_to_top_text }}</a></p>
+    {% endif %}
+
+    {{ footer_custom }}
+
+    {% if site.last_edit_timestamp or site.gh_edit_link or site.gh_offline_link %}
+      <div class="d-flex mt-2">
+        {% if site.last_edit_timestamp and site.last_edit_time_format and page.last_modified_date %}
+          <p class="text-small text-grey-dk-000 mb-0 mr-2">
+            Page last modified: <span class="d-inline-block">{{ page.last_modified_date | date: site.last_edit_time_format }}</span>.
+          </p>
+        {% endif %}
+        {% if
+          site.gh_edit_link and
+          site.gh_edit_link_text and
+          site.gh_edit_repository and
+          site.gh_edit_branch and
+          site.gh_edit_view_mode
+        %}
+          <p class="text-small text-grey-dk-000 mb-0{% if site.gh_offline_link and site.gh_offline_link_text and site.gh_offline_link_url %} mr-2{% endif %}">
+            <a href="{{ site.gh_edit_repository }}/{{ site.gh_edit_view_mode }}/{{ site.gh_edit_branch }}{% if site.gh_edit_source %}/{{ site.gh_edit_source }}{% endif %}{% if page.collection and site.collections_dir %}/{{ site.collections_dir }}{% endif %}/{{ page.path }}" id="edit-this-page">{{ site.gh_edit_link_text }}</a>
+          </p>
+        {% endif %}
+        {% if site.gh_offline_link and site.gh_offline_link_text and site.gh_offline_link_url %}
+          <p class="text-small text-grey-dk-000 mb-0">
+            <a href="{{ site.gh_offline_link_url }}" id="download-offline">{{ site.gh_offline_link_text }}</a>
+          </p>
+        {% endif %}
+      </div>
+    {% endif %}
+  </footer>
+{% endif %}