Quantecon-book-theme

This release has added codecov token explicitlt in codecov.yml , as codecov was complaining about it.
It also has following two features:
- Checking for mathjax version and using the config specified in `layout.html` when mathjax is of version 3. Users can use `mathjax_config` variable in `_config.yml` for version 2.
- Left-hand side menubar can now be made persistent across web pages using a config variable.

This release has fixes for the downlodPDFModal functionality and styling.

Has the following features and fixes:
- Collapsible input code blocks
- private input field in the launch dropdown menu for custom jupyterlab servers.
- mathjax config reading issue
- google analytics fix

Has the following fixes:

- Home button takes us to the global home page.
- Images in the lectures under the theme contained inside the margins.
- Correct font colors for dark mode.
- \boldsymbol tex package inclusion in mathjax.

This release includes a few refactoring, enhancements, and features:

- Upgraded to mathjax v3 from v2.
- Making interact feature of ipywidgets work with mathjax.
- Using web-compile https://github.com/executablebooks/web-compile to minify and hash css, js files. And create theme.conf file.
- Added tox.
- Reshuffling js files, and making tippy and feather work with it.
- Style changes in right navigation menu.
- Added UI to handle multiple launch buttons.
- Adding book and pdf download buttons.

Right sidebar navigation fix with numbering included.