[libc][docs] generate docs for ctype.h (llvm#87946)

Fixes llvm#87833

Author: zdumonts

libc/docs/ctype.rst

@@ -0,0 +1,53 @@
+ctype.h Functions
+=================
+
+.. list-table::
+  :widths: auto
+  :align: center
+  :header-rows: 1
+
+  * - Function
+    - Implemented
+    - Standard
+  * - isalnum
+    - |check|
+    - 7.4.1.1
+  * - isalpha
+    - |check|
+    - 7.4.1.2
+  * - isblank
+    - |check|
+    - 7.4.1.3
+  * - iscntrl
+    - |check|
+    - 7.4.1.4
+  * - isdigit
+    - |check|
+    - 7.4.1.5
+  * - isgraph
+    - |check|
+    - 7.4.1.6
+  * - islower
+    - |check|
+    - 7.4.1.7
+  * - isprint
+    - |check|
+    - 7.4.1.8
+  * - ispunct
+    - |check|
+    - 7.4.1.9
+  * - isspace
+    - |check|
+    - 7.4.1.10
+  * - isupper
+    - |check|
+    - 7.4.1.11
+  * - isxdigit
+    - |check|
+    - 7.4.1.12
+  * - tolower
+    - |check|
+    - 7.4.2.1
+  * - toupper
+    - |check|
+    - 7.4.2.2

libc/docs/index.rst

@@ -69,6 +69,7 @@ stages there is no ABI stability in any form.
    fenv
    libc_search
    c23
+   ctype
 
 .. toctree::
    :hidden:

libc/utils/docgen/ctype.json

@@ -1,7 +1,47 @@
 {
   "functions": {
-    "isalnum": null,
-    "isalpha": null,
-    "isblank": null
+    "isalnum": {
+      "defined": "7.4.1.1"
+    },
+    "isalpha": {
+      "defined": "7.4.1.2"
+    },
+    "isblank": {
+      "defined": "7.4.1.3"
+    },
+    "iscntrl": {
+      "defined": "7.4.1.4"
+    },
+    "isdigit": {
+      "defined": "7.4.1.5"
+    },
+    "isgraph": {
+      "defined": "7.4.1.6"	
+    },
+    "islower": {
+      "defined": "7.4.1.7"
+    },
+    "isprint": {
+      "defined": "7.4.1.8"
+    },
+    "ispunct": {
+      "defined": "7.4.1.9"
+    },
+    "isspace": {
+      "defined": "7.4.1.10"
+    },
+    "isupper": {
+      "defined": "7.4.1.11"
+    },
+    "isxdigit": {
+      "defined": "7.4.1.12"
+    },
+    "tolower" : {
+      "defined": "7.4.2.1"
+    },
+    "toupper": {
+      "defined": "7.4.2.2"
+    }
   }
 }
+