Add beginner tip to ErrorBoundary (#2385)

* Add beginner tip to ErrorBoundary

This might seem simple, but the nuances of types and traits confuse many people learning the language.

* edit

* Update error_boundary.rs

* edits

* ignore error block

leptos/src/error_boundary.rs

@@ -48,6 +48,28 @@ use leptos_reactive::{provide_context, run_as_child, signal_prelude::*};
 ///       {move || {
 ///   /* etc. */
 /// ```
+///
+/// ## Beginner's Tip: ErrorBoundary Requires Your Error To Implement std::error::Error.
+/// `ErrorBoundary` requires your `Result<T,E>` to implement [IntoView](https://docs.rs/leptos/latest/leptos/trait.IntoView.html).
+/// `Result<T,E>` only implements `IntoView` if `E` implements [std::error::Error](https://doc.rust-lang.org/std/error/trait.Error.html).
+/// So, for instance, if you pass a `Result<T,String>` where `T` implements [IntoView](https://docs.rs/leptos/latest/leptos/trait.IntoView.html)
+/// and attempt to render the error for the purposes of `ErrorBoundary` you'll get a compiler error like this.
+///
+/// ```rust,ignore
+/// error[E0599]: the method `into_view` exists for enum `Result<ViewableLoginFlow, String>`, but its trait bounds were not satisfied
+///    --> src/login.rs:229:32
+///     |
+/// 229 |                     err => err.into_view(),
+///     |                                ^^^^^^^^^ method cannot be called on `Result<ViewableLoginFlow, String>` due to unsatisfied trait bounds
+///     |
+///     = note: the following trait bounds were not satisfied:
+///             `<&Result<ViewableLoginFlow, std::string::String> as FnOnce<()>>::Output = _`
+///             which is required by `&Result<ViewableLoginFlow, std::string::String>: leptos::IntoView`
+///    ... more notes here ...
+/// ```
+///
+/// For more information about how to easily implement `Error` see
+/// [thiserror](https://docs.rs/thiserror/latest/thiserror/)
 #[component]
 pub fn ErrorBoundary<F, IV>(
     /// The components inside the tag which will get rendered