docs: make role of getQuartzComponents more clear and also make it optional

Jacky Zhao

2025-03-06 2213424195b6ba761a6bf3343afca43b102d06b3

 quartz/plugins/emitters/contentIndex.tsx

@@ -196,6 +196,5 @@
        }
      }
    },
    getQuartzComponents: () => [],
  }
}