[clang] [clang-repl] adding documentation and information for %commands (PR #150348)

[David Spickett via cfe-commits]

================
@@ -159,8 +159,31 @@ Lamdas:
    clang-repl> welcome();
    Welcome to REPL
 
-Using Dynamic Library:
-======================
+Comments:
+=========
+
+.. code-block:: text
+
+   clang-repl> // Comments in Clang-Repl
+   clang-repl> /* Comments in Clang-Repl */
+
+
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DavidSpickett wrote:

Remove the extra blank lines.

https://github.com/llvm/llvm-project/pull/150348