message: add description child
diff: # add release notes to the appdata file
  file(READ "${CHANGELOG_HTML}" HTML_CHANGELOGS)
  string(REPLACE "\n" "\n\t" RELEASES ${HTML_CHANGELOGS}) # add tabulator
  -string(REGEX REPLACE "<h3>(v[1-9]\\.[0-9]\\.[0-9]) - ([0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9])<\\/h3>" "<release version='\\1' date='\\2'>" RELEASES ${RELEASES})
  -string(REGEX REPLACE "<hr \\/>" "</release>" RELEASES ${RELEASES})
  +string(REGEX REPLACE "<h3>(v[1-9]\\.[0-9]\\.[0-9]) - ([0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9])<\\/h3>" "<release version='\\1' date='\\2'>\n\t<description>" RELEASES ${RELEASES})
  +string(REGEX REPLACE "<hr \\/>" "</description>\n\t</release>" RELEASES ${RELEASES})
  configure_file(${APPDATA_CONF} ${APPDATA})
  