Docs: add zh-CN entrypoint translations (#6300)

* Docs: add zh-CN entrypoint translations

* Docs: harden docs-i18n parsing

scripts/docs-i18n/placeholders.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+)
+
+type PlaceholderState struct {
+	counter int
+	used    map[string]struct{}
+}
+
+func NewPlaceholderState(text string) *PlaceholderState {
+	used := map[string]struct{}{}
+	for _, hit := range placeholderRe.FindAllString(text, -1) {
+		used[hit] = struct{}{}
+	}
+	return &PlaceholderState{counter: 900000, used: used}
+}
+
+func (s *PlaceholderState) Next() string {
+	for {
+		candidate := fmt.Sprintf("__OC_I18N_%d__", s.counter)
+		s.counter++
+		if _, ok := s.used[candidate]; ok {
+			continue
+		}
+		s.used[candidate] = struct{}{}
+		return candidate
+	}
+}