Add CHANGELOG for v0.4.0

Signed-off-by: Keshav Priyadarshi <git@keshav.space>

Author: keshav-space

CHANGELOG.rst

@@ -2,6 +2,15 @@ Changelog
 =========
 
 
+v0.4.0
+-------
+- FetchCode now supports retrieving package info for following generic packages: 
+    ``busybox``, ``bzip2``, ``dnsmasq``, ``dropbear``, ``ebtables``, ``hostapd``, ``ipkg``,
+    ``iproute2``, ``iptables``, ``libnl``, ``lighttpd``, ``nftables``, ``openssh``, ``samba``,
+    ``syslinux``, ``toybox``, ``uclibc``, ``uclibc-ng``, ``util-linux`` and ``wpa_supplicant``.
+- FetchCode also supports retrieving package info for GNU packages.
+
+
 v0.3.0
 -------
 - Add `package_versions` for retrieving all released versions of a given package.