feat(lib): add Jupyter magic (#237)

* feat(lib): add Jupyter magic

And also use the same logger level as manim (by default)

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix(lib): remove deleted module

* chore(lib): fix typing issues

* chore(docs): document magic

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix(ci): install kernel

* fix(ci): spawning is not necessary (and fails)

* chore(ci): add ipykernel

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

manim_slides/docs/manim_slides_directive.py

@@ -16,6 +16,17 @@ A directive for including Manim slides in a Sphinx document
 When rendering the HTML documentation, the ``.. manim-slides::``
 directive implemented here allows to include rendered videos.
 
+This directive requires three additional dependencies:
+``manim``, ``docutils`` and ``jinja2``. The last two are usually bundled
+with Sphinx.
+You can install them manually, or with the extra keyword:
+
+    pip install manim-slides[sphinx-directive]
+
+Note that you will still need to install Manim's platform-specific dependencies,
+see
+`their installation page <https://docs.manim.community/en/stable/installation.html>`_.
+
 Usage
 -----