dev-ml/*: improve metadata

Signed-off-by: Alessandro Barbieri <lssndrbarbieri@gmail.com>

dev-ml/xmlm/metadata.xml

@@ -1,4 +1,4 @@
-<?xml version='1.0' encoding='UTF-8'?>
+<?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
 <pkgmetadata>
 	<maintainer type="person">
@@ -6,7 +6,21 @@
 		<email>lssndrbarbieri@gmail.com</email>
 		<name>Alessandro Barbieri</name>
 	</maintainer>
+	<longdescription lang="en">Xmlm is a streaming codec to decode and encode the XML data format. It
+can process XML documents without a complete in-memory representation of the
+data.
+
+Xmlm is made of a single independent module and distributed
+under the ISC license.
+
+Home page: http://erratique.ch/software/xmlm</longdescription>
 	<upstream>
+		<doc>https://erratique.ch/software/xmlm/doc/</doc>
+		<bugs-to>https://github.com/dbuenzli/xmlm/issues</bugs-to>
 		<remote-id type="github">dbuenzli/xmlm</remote-id>
+		<maintainer>
+			<name>Daniel Bünzli</name>
+			<email>daniel.buenzli@erratique.ch</email>
+		</maintainer>
 	</upstream>
 </pkgmetadata>