support expressions and use them for links

exe/yamd

@@ -106,9 +106,13 @@ class HTMLRenderer < YAMD::Renderer
 		@buf << "</#{name}>"
 	end
 
-	def code(**attrs, &blk)
-		tag('pre') {
-			tag('code', **attrs) {
+	def link(to, &blk)
+		tag('a', href: to, &blk)
+	end
+
+	def code(&blk)
+		tag('pre', class: "language-any") {
+			tag('code', class: "language-any") {
 				@buf << YAMD::Code::highlight(blk.())
 			}
 		}
@@ -151,7 +155,7 @@ File.open(options[:in]) { |f|
 
 	renderer = HTMLRenderer.new
 
-	eval(code).(renderer)
+	renderer.instance_eval(code)
 
 	Pathname.new(options[:out]).write(renderer.finalize)
 }