Dyn load

[Baptistemontan]

• No static strings in the client binary
• Request translations using server fn
• Ship used translations with the HTML
• Fix "interpolate_display" feature
• Make it work with CSR
• Update docs

I'll write some docs for the book, but it won't be published so here is a few things to know about the newly added "dynamic_load" feature:

Translations are separated in what I call "translations units", if you don't use namespaces, there is one for each locale, if you use namespaces, the units are the product of namespaces and locales.
The feature remove the translations from the client binary, they are still embedded in the server binary. The server will send the used translations units (only the ones being used) in the sent html, they are parsed when the page hydrate.
When an t unit is used but still isn't loaded, a request is sent to the server and the view will update once that request returns.
For obvious reason, requesting the translations is async, so when using "dynamic_load", most variants of the t! macro will return a future:
t!, td! and tu! will still return a impl Fn() -> impl IntoView, the future is handled inside of it, so you don't need to update anything with those.
t*_string! and t*_display! return a impl Future, where the outputs are Cow<'static, str> and impl Display respectively, if you use those your code will need some updating.
If you use a backend where server functions need to be register manually, there is the ServerFn associated type on the Locale trait that the generated Locale enum implement thta you should register.

[Baptistemontan]

This is mostly working, two features are not compatible at the moment: "csr" and "interpolate_display"

[Baptistemontan]

Merging this, support for CSR will come later.