Support new LLM which is very popular and cheap in China: doubao

[AntiMoron]

As post title. And I like to contribute this one.

Doubao is the largest LLM in China which has 32 million daily active users. so just let you know, tons of Doubao fans out there in China, it can be great to enhance the brand awareness of RooCode in China region:

Once integrated Doubao, at least roocode website can gain traffic via SEO approaches. like "Doubao users can now use RooCode to have powerful vibe-coding!"

Doubao is also known as the volcengine, or Ark.(produced by bytedance, or simply consider it as Tiktok produced this LLM) See here: https://www.volcengine.com/experience/ark

I'm just a huge fan of it, wondering why the best LLM in China region not yet integrated, instead Deepseek did.

[AntiMoron]

#6345

Here's the MR

[AntiMoron]

I used Doubao to add those i18n text in this MR. Worked as expected.

Complete Tasks	Settings