jbig2dec: Fetch from GitHub

Closes: https://trac.macports.org/ticket/56562

Also add size to checksums.

graphics/jbig2dec/Portfile

@@ -1,7 +1,9 @@
 # -*- coding: utf-8; mode: tcl; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- vim:fenc=utf-8:ft=tcl:et:sw=4:ts=4:sts=4
 
 PortSystem          1.0
+PortGroup           github 1.0
 
+github.setup        ArtifexSoftware ghostpdl-downloads 922 gs
 name                jbig2dec
 version             0.14
 categories          graphics
@@ -23,11 +25,12 @@ long_description    JBIG2 is designed for lossy or lossless encoding \
                     JBIG2 features supported in PDF.
 
 homepage            https://artifex.com/developers-ghostscript-jbig2dec/
-# host downloads.ghostscript.com does not support https
-master_sites        http://downloads.ghostscript.com/public/jbig2dec/
+github.tarball_from releases
+distname            ${name}-${version}
 
 checksums           rmd160  c7421f9ff09bc125f3245ba7540fd969932ba8ab \
-                    sha256  21b498c3ba566f283d02946f7e78e12abbad89f12fe4958974e50882c185014c
+                    sha256  21b498c3ba566f283d02946f7e78e12abbad89f12fe4958974e50882c185014c \
+                    size    463572
 
 post-destroot {
     set docdir ${destroot}${prefix}/share/doc/${name}
@@ -39,3 +42,8 @@ post-destroot {
             README \
             ${docdir}
 }
+
+livecheck.type      regex
+livecheck.url       ${homepage}
+livecheck.version   ${version}
+livecheck.regex     /${name}-(\[0-9.\]+)${extract.suffix}