Clarify copyTo behavior in the documentation

Author: fzhinkin

core/common/src/Buffer.kt

@@ -205,6 +205,7 @@ public class Buffer : Source, Sink {
 
   /**
    * Copy bytes from this buffer's subrange starting at [startIndex] and ending at [endIndex], to [out] buffer.
+   * This method does not consume data from the buffer.
    *
    * @param out the destination buffer to copy data into.
    * @param startIndex the index (inclusive) of the first byte of data in this buffer to copy,

core/jvm/src/BufferExtJvm.kt

@@ -105,7 +105,8 @@ public fun Buffer.readTo(out: OutputStream, byteCount: Long = size) {
 }
 
 /**
- * Copy bytes from this buffer's subrange, starting at [startIndex] and ending at [endIndex], to [out].
+ * Copy bytes from this buffer's subrange, starting at [startIndex] and ending at [endIndex], to [out]. This method
+ * does not consume data from the buffer.
  *
  * @param out the destination to copy data into.
  * @param startIndex the index (inclusive) of the first byte to copy, `0` by default.