Document render_template(templates) list, closes #1045

docs/internals.rst

@@ -193,9 +193,11 @@ This method lets you read plugin configuration values that were set in ``metadat
 await .render_template(template, context=None, request=None)
 ------------------------------------------------------------
 
-``template`` - string
+``template`` - string or list of strings
     The template file to be rendered, e.g. ``my_plugin.html``. Datasette will search for this file first in the ``--template-dir=`` location, if it was specified - then in the plugin's bundled templates and finally in Datasette's set of default templates.
 
+    If this is a list of template file names then the first one that exists will be rendered.
+
 ``context`` - None or a Python dictionary
     The context variables to pass to the template.