Update NEWS / documentation with GC.start(compact:true)

NEWS.md

@@ -108,6 +108,14 @@ Outstanding ones only.
         * Symbol#to_proc now returns a lambda Proc.
           [[Feature #16260]]
 
+* GC
+
+    * Modified method
+
+        * GC.start now takes an option `compact: true` to compact the heap.
+          For example `GC.start(compact: true)` will have the same effect as
+          `GC.compact`.
+
 ## Stdlib updates
 
 Outstanding ones only.

gc.rb

@@ -26,6 +26,7 @@ module GC
   #
   #  Use full_mark: false to perform a minor GC.
   #  Use immediate_sweep: false to defer sweeping (use lazy sweep).
+  #  Use compact: true to compact the heap (it implies a full mark and sweep).
   #
   #  Note: These keyword arguments are implementation and version dependent. They
   #  are not guaranteed to be future-compatible, and may be ignored if the