docs: add bytedance-seed/seed-1.6-flash (#298)

Author: Lookoff-AIMLAPI

docs/SUMMARY.md

@@ -102,6 +102,7 @@
     * [Dola Seed 2.0 Code](api-references/text-models-llm/bytedance/dola-seed-2.0-code.md)
   * [ByteDance Seed](api-references/text-models-llm/ByteDance-Seed/README.md)
     * [Seed 1.6](api-references/text-models-llm/ByteDance-Seed/seed-1.6.md)
+    * [Seed 1.6 Flash](api-references/text-models-llm/ByteDance-Seed/seed-1.6-flash.md)
   * [Cohere](api-references/text-models-llm/Cohere/README.md)
     * [Command-a](api-references/text-models-llm/cohere/command-a.md)
   * [DeepSeek](api-references/text-models-llm/DeepSeek/README.md)