+ expose imaginary builtin

Author: skirpichev

peps/pep-0812.rst

@@ -227,9 +227,17 @@ Specification
 =============
 
 The :external+py3.14:ref:`imaginary literals <imaginary>` create instances of
-imaginary type, all values of this type could be represented as ``x*1j``, where
-``x`` is some :external+py3.14:class:`float` number.  So, strictly speaking, we
-need only one such object, the imaginary unit ``1j``, with a property:
+imaginary type:
+
+.. class:: imaginary(x=0.0)
+
+   Create an imaginary number from a number or a string.
+
+   This is equivalent of ``float(x)*1j``.
+
+
+Strictly speaking, we need only one such object, the imaginary unit ``1j``,
+with a property:
 
 .. code::
 
@@ -550,8 +558,8 @@ explain then a dedicated concept of imaginary numbers as a subtype of complex.
 Open Issues
 ===========
 
-The PEP doesn't expose a new subtype as a builtin, say ``imaginary``, but maybe
-we should?  This looks redundant, as all imaginary values could be obtained by
+The PEP expose a new subtype as the :class:`imaginary` builtin, but maybe we
+shouldn't?  This looks redundant, as all imaginary values could be obtained by
 scaling the imaginary unit, i.e. ``imaginary(x) == float(x)*1j``.