doc: Make "JSON" snippets valid JSON
doc: Make "JSON" snippets valid JSON

Documentation for `package.json`
[states](https://docs.npmjs.com/files/package.json) that it "must be actual
JSON, not just a JavaScript object literal".

PR-URL: https://github.com/npm/npm/pull/11196
Credit: da39a3ee5e6b4b0d3255bfef95601890afd80709@s100
Reviewed-By: da39a3ee5e6b4b0d3255bfef95601890afd80709@iarna

chadnickbok/npm,rsp/npm,lxe/npm,DaveEmmerson/npm,misterbyrne/npm,cchamberlain/npm,cchamberlain/npm,cchamberlain/npm-msys2,yibn2008/npm,TimeToogo/npm,yodeyer/npm,cchamberlain/npm-msys2,xalopp/npm,yodeyer/npm,Volune/npm,evocateur/npm,lxe/npm,evocateur/npm,TimeToogo/npm,lxe/npm,Volune/npm,yibn2008/npm,evocateur/npm,DIREKTSPEED-LTD/npm,misterbyrne/npm,Volune/npm,cchamberlain/npm-msys2,yodeyer/npm,chadnickbok/npm,midniteio/npm,DIREKTSPEED-LTD/npm,cchamberlain/npm,xalopp/npm,DIREKTSPEED-LTD/npm,chadnickbok/npm,yibn2008/npm,DaveEmmerson/npm,DaveEmmerson/npm,rsp/npm,TimeToogo/npm,misterbyrne/npm,midniteio/npm,rsp/npm,midniteio/npm,xalopp/npm