[libc] add doc for search.h (llvm#80492)

Author: SchrodingerZhu

libc/docs/index.rst

@@ -66,6 +66,7 @@ stages there is no ABI stability in any form.
    strings
    stdio
    stdbit
+   search
 
 .. toctree::
    :hidden:

libc/docs/search.rst

@@ -0,0 +1,71 @@
+=============
+Search Tables
+=============
+
+.. include:: check.rst
+
+---------------
+Source Location
+---------------
+
+-   The main source for bitwise utility functions is located at:
+    ``libc/src/search``.
+
+-   Hashtable implementation is located at:
+    ``libc/src/__support/HashTable``.
+
+-   The tests are located at:
+    ``libc/test/src/search/``.
+
+---------------------
+Implementation Status
+---------------------
+
+POSIX Standard Types
+====================
+
+============================ =========
+Type Name                    Available
+============================ =========
+ACTION                       |check|
+ENTRY                        |check|
+VISIT                        
+============================ =========
+
+POSIX Standard Functions
+========================
+
+============================ =========
+Function Name                Available
+============================ =========
+hcreate                      |check|
+hdestroy                     |check|
+hsearch                      |check|
+insque                       
+lfind                        
+lsearch                      
+remque
+tdelete
+tfind
+tsearch
+twalk
+============================ =========
+
+
+GNU Extension Functions
+=======================
+
+=========================  =========
+Function Name              Available
+=========================  =========
+hsearch_r                  |check|
+hcreate_r                  |check|
+hdestroy_r                 |check|
+tdestroy
+twalk_r
+=========================  =========
+
+
+Standards
+=========
+search.h is specified in POSIX.1-200x (Portable Operating System Interface, Volume1: Base Specifications).