The code in `navbar.dart' is now more declarative and cleaner.
If the `lastUpdate' variable’s content change, then it will force the
user to reload the page, bypassing their cache. This can be useful in
case of an update with which the cache could break the website.
This commit removes the `html' package dependency, speeding up the
compile time of the Dart code.
It also simplifies the code and removes some unused code. For instance
the sun, moon, and lightbulb icons is removed, the `Theme' class is
removed, and the `switchTheme' function is now merged into the
`setTheme' function. The `makeThemeItem' function has also had its
second argument removed.
Table of content was made unavailable regardless of whether one was
provided by the page or not. This commit fixes this issue by making an
unavailable TOC only if one is not provided by the web page, otherwise
the TOC will be available.
