Markdown doc content heading contains "" will be injected

[why520crazy]

Describe the bug
Heading contains "" will be injected.
https://github.com/docgeni/docgeni/blob/master/packages/core/src/markdown/renderer.ts#L33

To Reproduce

1. type '## Heading "xxx"' to any doc content

Expected behavior
Display '## Heading "xxx"'

Screenshots

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.