doc/melange.rst - make the alias attachment behavior of `melange.emit…

…` clearer (#7924)

* doc/melange.rst - make default target alias clear in introduction

Signed-off-by: Haochen Kotoi-Xie <hx@kxc.inc>

* reflect reviewer's comments and changes by #7926

Signed-off-by: Haochen Kotoi-Xie <hx@kxc.inc>

* fix formatting

Signed-off-by: Haochen Kotoi-Xie <hx@kxc.inc>

* reflect reviewer's comments

Signed-off-by: Haochen Kotoi-Xie <hx@kxc.inc>

* Update doc/melange.rst

Signed-off-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>

---------

Signed-off-by: Haochen Kotoi-Xie <hx@kxc.inc>
Signed-off-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>
Co-authored-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>

doc/melange.rst

@@ -57,8 +57,8 @@ Finally, add a source file to build:
 
   echo 'Js.log "hello from melange"' > hello.ml
 
-After running ``dune build output/hello.js``, Dune produces the following
-file structure:
+After running ``dune build @melange`` or just ``dune build``, Dune
+produces the following file structure:
 
 .. code::
 
@@ -148,6 +148,9 @@ 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.
 
+  - The targets of ``melange.emit`` are also attached to the Dune default
+    alias (``@all``), 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``.