Chinese about/feature-stages/index.md (#1917)
Chinese about/feature-stages/index.md (#1917)

- Translate feature stages into Chinese
- Refer to https://github.com/servicemesher/istio-official-translation/issues/111
linsun/istio.github.io,linsun/istio.github.io,istio/istio.io,istio/istio.io,linsun/istio.github.io,linsun/istio.github.io,istio/istio.io,geeknoid/istio.github.io,istio/istio.io,geeknoid/istio.github.io,linsun/istio.github.io,geeknoid/istio.github.io,istio/istio.io,istio/istio.io,geeknoid/istio.github.io,geeknoid/istio.github.io,istio/istio.io