v0.4.0 release (icaros-usc#170)

* Bump version: 0.3.1 → 0.4.0

* Update HISTORY

Run actions on tags

Bump version: 0.2.1 → 0.3.0

Miscellaneous docs fixes (icaros-usc#67)

* Fix time in lunar lander tutorial

* Ignore results dirs

* Fix GitHub Actions link in README

* Fix sidebar color in code cells

* Fix github link in README

* Tweak README credits

* Add css selection rule

* Remove global toc header

* Add pyribs email for author

* Disable tagging for bump2version

* Remove last updated date

* Update deployment process

* Add 404 page

* Allow different URLs based on readthedocs env

* Correct readthedocs version in url

* Change OpenGraph image filename

* Customize ReadTheDocs flyout

* Remove OpenGraph description as it is blank

* Use just 1 emitter in Fooling MNIST

* Update history for 0.2.1

* Bump version: 0.2.0 → 0.2.1

Bump version: 0.1.1 → 0.2.0