include flush root render method to createFormControl

[bluebill1049]

ref: https://codesandbox.io/s/friendly-euler-0mrm0z?file=/src/App.tsx

[codesandbox]

  Open in CodeSandbox Web Editor | VS Code | VS Code Insiders

[github-actions]

Size Change: +37 B (0%)

Total Size: 18.5 kB

Filename	Size	Change
dist/index.cjs.js	9.21 kB	+30 B (0%)
dist/index.umd.js	9.3 kB	+7 B (0%)

_{compressed-size-action}