howto_release.txt: +i18N .po file update procedure

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@72341 15284696-431f-4ddb-bdfa-cd5b030d7da7

doc/howto_release.txt

@@ -23,6 +23,13 @@ Contents
 # fix typos in source code with 
 tools/fix_typos.sh
 
+# i18N: sync from Transifex (https://www.transifex.com/grass-gis/grass72/dashboard/)
+#  - except for Latvian; Latvian is directly edited in SVN and then sync'ed from trunk .po files
+cd locale
+sh ~/software/grass-addons/tools/transifex_merge.sh
+make
+make verify
+# ... then fix .po files as needed.
 
 1. Local work