fix most typos, add crate-ci/typos to CI (#2653)

* fix most typos, add crate-ci/typos to CI

---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

examples/signals.rs

@@ -1,6 +1,6 @@
 //! A simple example demonstrating how to use signals to modify state from several different places.
 //!
-//! This simlpe example implements a counter that can be incremented, decremented, and paused. It also demonstrates
+//! This simple example implements a counter that can be incremented, decremented, and paused. It also demonstrates
 //! that background tasks in use_futures can modify the value as well.
 //!
 //! Most signals implement Into<ReadOnlySignal<T>>, making ReadOnlySignal a good default type when building new