Add *.xhtm file extension

AlexxNB · web-flow · commit 1ea9bbf7d24d · 2020-07-29T16:57:21.000+03:00
`xhtm` - is also valid file extension for XHTML files. It is like `htm` and `html` for HTML.
diff --git a/extensions/html/package.json b/extensions/html/package.json
@@ -20,6 +20,7 @@
           ".htm",
           ".shtml",
           ".xhtml",
+          ".xhtm",
           ".mdoc",
           ".jsp",
           ".asp",
