Update all docs links to 0.6, release 0.6 (#3225)

* update doc links to 0.6
* add new splash pages for crates
* update keyword features
* remove some unnecessary links

packages/signals/src/read_only_signal.rs

@@ -11,6 +11,9 @@ pub struct ReadOnlySignal<T: 'static, S: Storage<SignalData<T>> = UnsyncStorage>
     inner: Signal<T, S>,
 }
 
+/// A signal that can only be read from.
+pub type ReadSignal<T, S> = ReadOnlySignal<T, S>;
+
 impl<T: 'static, S: Storage<SignalData<T>>> From<Signal<T, S>> for ReadOnlySignal<T, S> {
     fn from(inner: Signal<T, S>) -> Self {
         Self { inner }