Improve error messages.

Author: leerho

src/main/java/org/apache/datasketches/quantiles/DoublesSketch.java

@@ -158,7 +158,9 @@ public static DoublesSketch heapify(final MemorySegment srcSeg) {
    */
   public static DoublesSketch wrap(final MemorySegment srcSeg) {
     if (!checkIsMemorySegmentCompact(srcSeg)) {
-      throw new SketchesArgumentException("MemorySegment sketch image must be in compact form.");
+      throw new SketchesArgumentException(
+          "MemorySegment sketch image must be in compact form. " 
+      + "Use {@link #writableWrap(MemorySegment writableWrap(...)} for updatable sketches.");
     }
     return DirectCompactDoublesSketch.wrapInstance(srcSeg);
   }
@@ -179,7 +181,9 @@ public static DoublesSketch wrap(final MemorySegment srcSeg) {
    */
   public static DoublesSketch writableWrap(final MemorySegment srcSeg) {
     if (checkIsMemorySegmentCompact(srcSeg)) {
-      throw new SketchesArgumentException("MemorySegment sketch image must be in updatable form.");
+      throw new SketchesArgumentException(
+          "MemorySegment sketch image must be in updatable form. " 
+      + "Use {@link #wrap(MemorySegment writableWrap(...)} for compact sketches.");
     }
     return DirectUpdateDoublesSketch.wrapInstance(srcSeg, null);
   }