refactor i18n yaml to prevent overwriting parent non-English YAML with local English file: metanorma/isodoc#549

Author: opoudjis

lib/isodoc/iso/i18n.rb

@@ -8,7 +8,7 @@ def load_file(fname)
 
       def load_yaml1(lang, script)
         y = load_file("i18n-#{yaml_lang(lang, script)}.yaml")
-        super.deep_merge(y)
+        y.empty? ? load_file("i18n-en.yaml").merge(super) : super.deep_merge(y)
       end
     end
   end

spec/isodoc/i18n_spec.rb

@@ -549,10 +549,12 @@
           <bibdata>
            <status>
              <stage abbreviation='IS' language=''>60</stage>
+             <stage abbreviation="IS" language="tlh">International Standard</stage>
            </status>
            <language current='true'>tlh</language>
            <ext>
              <doctype language=''>international-standard</doctype>
+             <doctype language="tlh">International Standard</doctype>
            </ext>
          </bibdata>
           <preface>