Packaging cleanup

* Declare compliance with policy 4.6.0
* Bump debhelper compat level to 13
* Update debian/watch to version 4 and follow upstream changes

debian/control

@@ -1,10 +1,10 @@
 Source: jose
 Maintainer: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
 Homepage: https://github.com/latchset/jose
-Standards-Version: 4.5.0
+Standards-Version: 4.6.0
 Vcs-Browser: https://git.in-ulm.de/cbiedl/jose
 Vcs-Git: https://git.in-ulm.de/cbiedl/jose.git
-Build-Depends: debhelper-compat (= 12),
+Build-Depends: debhelper-compat (= 13),
     libjansson-dev (>= 2.10),
     libssl-dev (>= 1.0.2),
     pkg-config,

debian/watch

@@ -1,4 +1,4 @@
 
-version=3
+version=4
 https://github.com/latchset/jose/releases \
-    /latchset/jose/releases/download/[^/]+/jose-([0-9][.0-9]*)\.tar\.bz2
+    /latchset/jose/releases/download/v[0-9]+/jose-([0-9][.0-9]*)@ARCHIVE_EXT@