improved Dutch translations

[PanderMusubi]

For almost fifteen years, I have been maintaining https://github.com/PanderMusubi/dutch-holidays (which was also used by Thunderbird) and would like to contribute to this project and slowly move the relevant data to here.

[ehoogeveen-medweb]

Looks good to me except for O.L.V. Hemelvaart and O.L.H. Hemelvaart, have a look at my comments and let me know what you think!

[PanderMusubi]

O.L.H.

yep, fixed it in next commit the way you proposed it, now I see Hemelvaartsdag in the NL.,yml file.

[PanderMusubi]

@ehoogeveen-medweb what do you think about adding these local days to observe:

• Alkmaars Ontzet
• Gronings Ontzet
• Leids Ontzet
• Inname van Den Briel

as they have a major impact on local businesses and local infrastructure

How about these national days that have impact on a national level:

• Ketikoti
• Wintertijd (uur achteruit)
• Zomertijd (uur vooruit)

The following national one, but if they are not to be included, also not include Koninkrijksdag:

• Naturalisatiedag
• Veteranendag

And these international days that have impact on infrastructure:

• Halloween
• Black Friday
• Internationale Vrouwendag
• Secretaressedag

[commenthol]

Can you please run the (re-) generation of the test fixtures as stated in CONTRIUTING.md? Thanks.

npx mocha test/all.mocha.js --writetests --countries NL

[PanderMusubi]

Can you please run the (re-) generation of the test fixtures as stated in CONTRIUTING.md? Thanks.

npx mocha test/all.mocha.js --writetests --countries NL

thanks, done

[ehoogeveen-medweb]

@ehoogeveen-medweb what do you think about adding these local days to observe:

* Alkmaars Ontzet
* Gronings Ontzet
* Leids Ontzet
* Inname van Den Briel

as they have a major impact on local businesses and local infrastructure

Being local days, it might make sense to add them in states or regions (see e.g. the German data).

How about these national days that have impact on a national level:

* Ketikoti
* Wintertijd (uur achteruit)
* Zomertijd (uur vooruit)

Ketikoti is already in there, right? I don't think there's a precedent for including DST changes, but I could be wrong. They don't seem like they fit any definition of holidays at least.

The following national one, but if they are not to be included, also not include Koninkrijksdag:

* Naturalisatiedag
* Veteranendag

I think it's fine to include these as observance type holidays.

And these international days that have impact on infrastructure:

* Halloween
* Black Friday
* Internationale Vrouwendag
* Secretaressedag

Same with these, though I don't know where to draw the line with regard to international days (since it seems like people keep making up more). I guess the question is whether people take the day off for them - though for something like Halloween, it seems more likely that people would take the next day off.