clang-format: [JS] document InsertTrailingCommas.

[mprobst]

Summary

In release notes and the regular docs.

[MyDeveloperDay]

LGTM thank you

[MyDeveloperDay]

I'm trying to prevent this from getting deleted in D78982: [clang-format] Fix Microsoft style for enums

@mprobst When you added this documentation did you add it to Format.h and regenerate the rst text.

ClangFormatStyleOptions.rst should be generated using the clang/docs/tools/dump_format_style.py

clang/docs/ClangFormatStyleOptions.rst

.. code-block:: c++
 
     false:
     void f() {
       f(aaaaaaaaaaaaaaaaaaaa,
         aaaaaaaaaaaaaaaaaaaa,
         aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);
     }
 
+
+**InsertTrailingCommas** (``TrailingCommaStyle``) can be set to ``TCS_Wrapped``
+  to insert trailing commas in container literals (arrays and objects) that wrap
+  across multiple lines. It is currently only available for JavaScript and
+  disabled by default (``TCS_None``).
+
+  ``InsertTrailingCommas`` cannot be used together with ``BinPackArguments`` as
+  inserting the comma disables bin-packing.
+
+  .. code-block:: c++
+
+    TSC_Wrapped:
+    const someArray = [
+      aaaaaaaaaaaaaaaaaaaaaaaaaa,
+      aaaaaaaaaaaaaaaaaaaaaaaaaa,
+      aaaaaaaaaaaaaaaaaaaaaaaaaa,
+      //                        ^ inserted
+    ]
+
+
 **BinPackParameters** (``bool``)
   If ``false``, a function declaration's or function definition's
   parameters will either all be on the same line or will have one line each.
 
   .. code-block:: c++
 
     true:
     void f(int aaaaaaaaaaaaaaaaaaaa, int aaaaaaaaaaaaaaaaaaaa,

clang/docs/ReleaseNotes.rst

case 1:                                case 1: {
       }                                    default: {
       break;                                 plop();
     default:                               }
       {                                    }
         plop();
       }
     }
 
+- Option ``InsertTrailingCommas`` can be set to ``TCS_Wrapped`` to insert
+  trailing commas in container literals (arrays and objects) that wrap across
+  multiple lines. It is currently only available for JavaScript and disabled by
+  default (``TCS_None``).
+
 libclang
 --------
 
 - ...
 
 Static Analyzer
 ---------------