Add npm `minimum-release-age` and `sfw` (incl. aliases)

[karlhorky]

pnpm usage already has security settings configured (as well as the secure defaults for other config settings):

• Configure 7 day minimumReleaseAge for pnpm #107

We recommend students use pnpm, but students may follow guides online which use npm without noticing the difference.

npm is still a bit behind in terms of supply chain security, but we can achieve some security with sfw:

• npm config set min-release-age=7
• npm install -g sfw
• alias npm="sfw npm"
• alias pnpm="sfw pnpm"