`translatable` node is not documented on the page 'Doctree node classes added by Sphinx'

[igo95862]

This node allows supplying custom translation strings.

Link to source:

sphinx/sphinx/addnodes.py

Line 47 in 996c585

class translatable(nodes.Node):

It is not present on the Doctree node classes added by Sphinx nor i18n API.

[terminalchai]

Opened #14348 to document sphinx.addnodes.translatable in the doctree node reference and i18n API docs.