d/gbp.conf: Automatically bump meson.build version

No more manual editing.
Signed-off-by: Guido Günther <guido.gunther@puri.sm>

debian/gbp.conf

@@ -5,3 +5,6 @@ debian-tag-msg = %(pkg)s v%(version)s
 
 [tag]
 sign-tags = true
+
+[dch]
+postedit = sed -i s"@^\( \+version: '\)[0-9.]\+\(',\)@\1$GBP_DEBIAN_VERSION\2@" meson.build