[GpgOL] Providing Dutch (nl) translation

Hello,

As a big fan of Outlook, Dutch translations and of course GPG, I am a daily
user of GpgOL. I noticed that there is no Dutch translation available for
this software, so I decided to contribute to the project.

For my own convenience, I have created a fork on GitHub and committed my
changes there. You are probably only interested in [1]. I have tried to use
the same translations as used in Kleopatra, to keep the user experience
consistent. Unfortunately, I was not able to compile a working version of de
add-on, so I could not check if all strings fit within the UI.

If you decide to add Dutch, I will try to keep the translations up-to-date
with your ongoing development. What will be the preferred way of providing
new translations? Attaching patch files to an email on this mailing list, as
I see mostly done in the archives of this list?

Kind regards,

Erwin Bronkhorst

[1] https://github.com/EagleErwin/gpgol/blob/dutch/po/nl.po