bpo-28331: fix impl-detail label is removed when content is translated. (GH-195)

diff --git a/Doc/tools/templates/dummy.html b/Doc/tools/templates/dummy.html
new file mode 100644
index 0000000..6e43be2
--- /dev/null
+++ b/Doc/tools/templates/dummy.html
@@ -0,0 +1,6 @@
+This file is not an actual template, but used to add some
+texts in extensions to sphinx.pot file.
+
+In extensions/pyspecific.py:
+
+{% trans %}CPython implementation detail:{% endtrans %}