reflect reviewer's comments and changes by ocaml#7926

Signed-off-by: Haochen Kotoi-Xie <[email protected]>

Author: haochenx

doc/melange.rst

@@ -57,10 +57,8 @@ Finally, add a source file to build:
 
   echo 'Js.log "hello from melange"' > hello.ml
 
-After running ``dune build output/hello.js`` or ``dune build @melange``
-(by default, all ``melange.emit`` stanzas will attach their targets to
-the  ``melange`` alias),
-Dune produces the following file structure:
+After running ``dune build output/hello.js``, Dune produces the following
+file structure:
 
 .. code::
 
@@ -150,6 +148,10 @@ The resulting layout in ``_build/default/output`` will be as follows:
     is explicitly defined in the stanza, the targets from this stanza will
     be excluded from the ``melange`` alias.
 
+  - As per Dune's convention, all targets declared using this stanza will also
+    be attached to the Dune's default `@all` alias, regardless of whether
+    the `(alias ...)` field is present.
+
 - ``(module_systems <module_systems>)`` specifies the JavaScript import and
   export format used. The values allowed for ``<module_systems>`` are ``es6``
   and ``commonjs``.