docs: Split as-module into smaller documents

docs/module/nodeiterator.rst

@@ -0,0 +1,31 @@
+Resumable Iterations
+^^^^^^^^^^^^^^^^^^^^
+
+.. module:: instaloader
+   :noindex:
+
+.. highlight:: python
+
+.. contents::
+   :backlinks: none
+
+For many download targets, Instaloader is able to resume a
+previously-interrupted iteration. It provides an interruptable
+Iterator :class:`NodeIterator` and a context manager
+:func:`resumable_iteration`, which we both present here.
+
+.. versionadded:: 4.5
+
+``NodeIterator``
+""""""""""""""""
+
+.. autoclass:: NodeIterator
+   :no-show-inheritance:
+
+.. autoclass:: FrozenNodeIterator
+   :no-show-inheritance:
+
+``resumable_iteration``
+"""""""""""""""""""""""
+
+.. autofunction:: resumable_iteration