Automatically solve conflict in package.json

Description

When package.json merging conflict happens, code-sync will break down, we need to automatically solve conflict on this file.

Proposal

Using ours merging strategy as same as yarn.lock do, when merge done, checkout upstream package.json concat jh/frontend.json (added in gitlab!860 (merged)) with it.

If some package exist both in package.json and jh/frontend.json, use the upstream version, CI job mentioned in gitlab#1748 (closed) will throw error to ask developers change conflicted package names to alias, and refactor the name in js code