misc: npmignore larger unnecessary files

[brendankenny]

going through our npm packed files, a few more large ones jumped out that aren't needed for a production run (basically all the files >100KiB that aren't a locale file):

• one of the recipes under docs/
• prebuilt json schemas under sd-validation/
• our 360KiB (and growing) changelog

npmignoring these saves about 1MiB in our installed package size (package size: 2.5 MB -> 2.2 MB, unpacked size: 12.6 MB -> 11.6 MB).

I never go into an installed package to get docs about that package (I go to npm or direct to the repo), but if that is a use case worth preserving we could ignore just docs/recipes/ and keep the changelog and still get like half of the savings.

[brendankenny]

ping @connorjclark :)