Merge pull request jupyter-book#2083 from executablebooks/dependabot/…

…github_actions/actions/checkout-4

build(deps): bump actions/checkout from 3 to 4

RELEASE: v0.15.1 + BUG: Issue warning for sphinxcontrib-bibtex + docu…

…tils>=0.18,<0.20 (jupyter-book#1965)

* pin docutils < 0.18 (mcmtroffaes/sphinxcontrib-bibtex#322)

* Prep for v0.15.1

* rework, issue warning rather than force version pin on docutils

* only test html if no warnings

* doc: add entry for citations page

* update changelog

RELEASE: v0.15.0 (jupyter-book#1963)

* RELEASE: v0.15.0

* review docs related to theme keyword

DOCS: Fix table and formatting in CHANGELOG (jupyter-book#1947)

* DOCS: fix minor table formatting issue in CHANGELOG

* update to format

Release v0.13.2 (jupyter-book#1927)

[Release] Prepare for v0.13.1 (jupyter-book#1809)

RELEASE: v0.13.0 (jupyter-book#1739)

* RELEASE: v0.13.0

* fix typo

* Update CHANGELOG.md

Co-authored-by: Chris Holdgraf <[email protected]>

Co-authored-by: Chris Holdgraf <[email protected]>

RELEASE: v0.12.3 (jupyter-book#1682)

RELEASE: v0.12.2 (jupyter-book#1641)

RELEASE: Setup and Changes for v0.12.1 (jupyter-book#1542)