* create 3.4.x navigation
* add content related to multi-credential management and load balancing for 3-5-x
* add content related to knowledge pipeline for 3-6-x
* add content related to trigger, multimodal embedding, and json object for 3-7-x
* changes upon review
* remove unnecessary links
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Co-authored-by: Riskey <riskey47@dify.ai>
