on the main page you can add information for a name if you go through the 'submit a name' and then go to 'correct an existing name', you could also e-mail Mike
if you have a long list. Also adding them to the 'comments' section would be useful, since that's where people tend to look for pronunciations if it isn't with the name.
about the pronunications:
I'd say that the pronunciations for Heike
are pretty much the same as the German
ones, the EI (or IJ for that matter) would be like something in between IE and EY, so HIE-ku would be valid as well (same thing for Eilert
, I'd write that as IE-lurt). And for Dieuwke
, I would say it's pronounced more like: DEEOOW-ku / DEEW-ku, because with DEW-ku, you can't hear the 'i' that is in there.
would be YAH-pik (because otherwise you'd get something like djapik (Dutch pron.) if you know what I mean).