[libc] Generate docs for setjmp.h (#89542)

Resolves #88065

Added macros and functions.

Author: Rajveer100

libc/docs/index.rst

@@ -72,6 +72,7 @@ stages there is no ABI stability in any form.
    ctype
    signal
    threads
+   setjmp
 
 .. toctree::
    :hidden:

libc/docs/setjmp.rst

@@ -0,0 +1,16 @@
+.. include:: check.rst
+
+setjmp.h Functions
+==================
+
+.. list-table::
+  :widths: auto
+  :align: center
+  :header-rows: 1
+
+  * - Function
+    - Implemented
+    - Standard
+  * - longjmp
+    - |check|
+    - 7.13.2.1

libc/utils/docgen/setjmp.json

@@ -0,0 +1,15 @@
+{
+  "macros": {
+    "__STDC_VERSION_SETJMP_H__": {
+      "defined": "7.13.2"
+    },
+    "setjmp": {
+      "defined": "7.13.1.1"
+    }
+  },
+  "functions": {
+    "longjmp": {
+      "defined": "7.13.2.1"
+    }
+  }
+}