Lilypond-book: Document htmly as allowed extension for HTML

diff --git a/Documentation/usage/lilypond-book.itely b/Documentation/usage/lilypond-book.itely
index 4a2f9181a4320ab53538733d01a3e246e14611da..daf9b4dcfde9e22a73f2188f4039e6dd9d50d768 100644 (file)
--- a/Documentation/usage/lilypond-book.itely
+++ b/Documentation/usage/lilypond-book.itely
@@ -971,6 +971,7 @@ selects the output format based on the input filename's extension.
 @item @strong{extension} @tab @strong{output format}
 @item
 @item @file{.html} @tab HTML
+@item @file{.htmly} @tab HTML
 @item @file{.itely} @tab Texinfo
 @item @file{.latex} @tab @LaTeX{}
 @item @file{.lytex} @tab @LaTeX{}