Add documentation for symbol search workflow in chat

Author: jdorfman

docs/omnibox/query-types/symbol-search.mdx

@@ -1 +1,15 @@
 # Symbol Search
+
+<p className="subtitle">Symbol Search is a query type or workflow that helps developers understand how specific symbols (like functions, variables, or hooks) are used across a codebase by combining search results with contextual analysis through chat.</p>
+
+It enables developers to explore and understand symbol usage patterns through a two-step process. First, developers search for a specific symbol (like `useCallback`) using Sourcegraph Chat, which returns relevant code snippets from across the codebase. These search results are automatically preserved as context for follow-up chat interactions. Developers can then refine their understanding by selecting specific search results and asking natural language questions about the symbol's usage patterns. The chat will analyze the selected code context and provide a comprehensive summary of how the symbol is implemented and used throughout the codebase.
+
+### Try it
+
+1. Query for `= useCallback`
+2. Select a subset of the search results which include usage for `useCallback`
+3. Follow up and ask Sourcegraph chat `Summarize how useCallback is used`
+
+### Demo
+ 
+🔴 Waiting for UI to update 🔴