[why]
Somebody might want to have a file where all symbols we add are listed.
At the moment there are only the i_*.sh scripts and the CSS files. Both
are rather unwieldy.
[how]
Just create a json file with all symbol names, like the CSS file.
Fixes: #448
Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>
