Move "Developer Guide" from Docs to Community

[wuchong]

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Description

The "Developer Guide", which includes sections such as "Building Fluss from Source" and "Import Fluss into an IDE", is currently located under the website/docs/* directory. However, these guides are not tied to any specific version of Fluss and are primarily intended for contributors rather than end users. As such, they are better suited for the Community Documentation (website/community/*) section, which focuses on resources for the contributor community.

Willingness to contribute

• I'm willing to submit a PR!

[gyang94]

Hi @wuchong , I made a PR #539 to move "Developer Guide" to community.
I am not sure where is the good place to put those content, either in "how to contribute" section or just make it an standalone section.
Now I just put it as a standalone section. It is the forth item in the sidebar. Like this: