Add note regarding null as a reserved value in object mode

Author: kgryte

lib/node_modules/@stdlib/streams/node/from-constant/README.md

@@ -194,6 +194,7 @@ This method accepts the same `options` as [`constantStream()`](#constant-stream)
 ## Notes
 
 -   In binary mode, a provided `value` must be a `string`, `Buffer`, or `Uint8Array`.
+-   In [`objectMode`][object-mode], `null` is a reserved value. If provided `null`, the returned [stream][stream] will prematurely end.
 -   If provided an `object` reference, the `value` is **not** copied. To avoid unwanted mutation, copy the `value` **before** creating a [stream][stream].
 -   In older Node.js environments, `Uint8Array` contents may be copied to a new `Buffer` object due to changes in the underlying Node.js APIs.
 -   If the `factory` method is provided only one argument and that argument is an `object` (either empty or not containing any recognized `options` properties), the method treats the argument as a value to be streamed, **not** as an `options` argument.

lib/node_modules/@stdlib/streams/node/from-constant/docs/repl.txt

@@ -2,6 +2,9 @@
 {{alias}}( value[, options] )
     Returns a readable stream which always streams the same value.
 
+    In object mode, `null` is a reserved value. If provided `null`, the
+    returned stream will prematurely end.
+
     Parameters
     ----------
     value: string|Buffer|Uint8Array|any
@@ -98,6 +101,9 @@
 {{alias}}.objectMode( value[, options] )
     Returns an "objectMode" readable stream which always streams the same value.
 
+    In object mode, `null` is a reserved value. If provided `null`, the
+    returned stream will prematurely end.
+
     Parameters
     ----------
     value: any