feat: better import dsl on GitHub

[yihong0618]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

for now, import dsl on GitHub only can use raw url like https://raw.githubusercontent.com/Winson-030/dify-DSL/refs/heads/main/SearchAgent.yml
but when user is likely to use is import https://github.com/Winson-030/dify-DSL/blob/main/SearchAgent.yml
we can do some trick to replace the url to better user experience

2. Additional context or comments

No response

3. Can you help us with this feature?

• I am interested in contributing to this feature.

[laipz8200]

Sounds good to me!