Standard javascript tools add newline at the end of file of package.json.
yarnpkg/yarn#2675

Current behavior:
wasm-pack does not add newline at the end of file of the generated package.json files.

Requested behavior:
add newline at the end of file of the generated package.json files.

Why?
Current behavior leads to frequent diff when the generated package.json is included in the git repository, as the newline is either added or removed every time you run wasm-pack or yarn