Performance improvement on start

[rhysd]

• Profiling main and renderer process
• Remove useless initialization
• Defer some initializations at start

[rhysd]

We should do

• [x] defer mermaid.js initialization
• [x] reduce calling ipc.sendSync()
• [x] defer creating <webview>

Total: 3357.529ms

[rhysd]

• [x] Execute linter without IPC blocking