match other common markdown file extensions

diff --git a/filters/about-formatting.sh b/filters/about-formatting.sh
index 892fbeb7a7933b0f33dca4f9e3162dc27cfc94ad..d0242047c1007e01b911853827db292bfbcfbd40 100755 (executable)
--- a/filters/about-formatting.sh
+++ b/filters/about-formatting.sh
@@ -19,7 +19,7 @@
 
 cd "$(dirname $0)/html-converters/"
 case "$(printf '%s' "$1" | tr '[:upper:]' '[:lower:]')" in
-       *.md|*.mkd) exec ./md2html; ;;
+       *.markdown|*.mdown|*.md|*.mkd) exec ./md2html; ;;
        *.rst) exec ./rst2html; ;;
        *.[1-9]) exec ./man2html; ;;
        *.htm|*.html) exec cat; ;;