Add documentation/guidelines for site integration using SSR and Fetch/XHR API detection

Description

When adding support for new websites that utilize Server-Side Rendering (SSR), checking for username existence by analyzing the returned initial HTML page often fails. In many SSR architectures, user-specific search results or profile states are loaded asynchronously after the initial page shell is delivered.

Specifically:

SSR Awareness: Clarify that for SSR-enabled sites, raw HTML responses from the base URL may not contain profile/user existence data.

API-based Detection: Instruct contributors to rely on internal API endpoints (JSON responses) instead of page HTML for username checking.

Inspection Workflow: Document the exact steps for finding these endpoints:

Open Developer Tools (F12).

Navigate to the Network (网络) tab.

Filter requests by Fetch/XHR.

Refresh the page or trigger the search action to capture the underlying API requests and payload structures.

Code of Conduct

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