add a lua version

filter.lua

@@ -0,0 +1,20 @@
+function File2Block(filename)
+    local fh = io.open(filename, "r")
+    if not fh then
+        io.stderr:write("Cannot open file: " .. filename .. "\n")
+        return { pandoc.Plain { pandoc.Str("[Error: cannot read file " .. filename .. "]") } }
+    end
+    local contents = fh:read("*a")
+    fh:close()
+    return { pandoc.Plain { pandoc.Str(contents) } }
+end
+
+function Div(e)
+    local include = e.attributes["include"]
+    if include then
+        local blocks = File2Block(include)
+        -- Replace the Div contents
+        return pandoc.Div(blocks, e.attr)
+    end
+    return nil -- no change
+end