Add charset check in Syncer precheck (#1300)
Add charset check in Syncer precheck (#1300)

* Add charset check in Syncer precheck

* Update tools/syncer.md

Co-Authored-By: ericsyh <cc85f6cea4f666b754bfb07ef0e90d9fc50f877c@outlook.com>

pingcap/docs-cn,pingcap/docs-cn