Amend RFC 0724 to include template type checking

RFC #724 originally intentionally excluded template type checking via
Glint from its designation of "official support" for Ember. However, in
the time since the RFC was authored, there have been two significant changes:

1.  Glint itself has matured significantly, with no known major issues
    at this time (though plenty of polish still to be done).

2.  The *major* design issues in Ember needed to unblock Glint have
    been resolved:

    - resolution of template identifiers (components, helpers, and
      modifiers): RFC #779
    - a Glimmer Component type signature which exposes information
      about the blocks and the target for `...attributes`: RFC #748

Although there remain a number of smaller design questions to resolve,
this is sufficient for us to treat type-checked templates as a viable
part of our story, and given *viability*, we think this is *necessary*.

Author: chriskrycho

text/0724-road-to-typescript.md

@@ -122,9 +122,7 @@ Additionally, this RFC does not propose changing the *default* experience from J
 
 #### Typed Templates
 
-This roadmap RFC explicitly does not require support for “typed templates” as part of the path to adopting TypeScript as a community. TypeScript-powered integration between the template layer and the JavaScript context is a key goal for the Typed Ember team already. However, it is not a *gating feature* for Ember to officially support TypeScript. Rather: the feature can be rolled out and integrated with Ember CLI, the Ember Language Server, and other tooling whenever it is ready, decoupled from the other efforts here. If we reach a point where full support for type-aware template integration exists and is sufficiently robust, we can consider adding it to our definition of official Ember support via a dedicated RFC.
-
-The *only* relationship those efforts have to this roadmap is that they will inform the design of the `@glimmer/component@2.x` TypeScript API (as described below under **Roadmap**).
+Given the importance of templates in Ember and Glimmer apps, “typed templates” are a key part of the path to adopting TypeScript as a community. TypeScript-powered integration between the template layer and the JavaScript context is a key goal for the Typed Ember team already. It is not a *gating feature* for Ember packages to officially supply TypeScript. Instead: the feature can be rolled out and integrated with Ember CLI, the Ember Language Server, and other tooling whenever it is ready, decoupled from the other efforts here. However, given its importance as one of the primary API boundaries within Ember and Glimmer apps, our definition of official Ember support would be incomplete without it.
 
 
 ### Roadmap
@@ -179,6 +177,10 @@ There are also a number of key implementation concerns which must be addressed,
 
 - **How do app and addon authors *consume* published types?** There are a few “gotchas” about how TypeScript supports features like autocomplete in a project, which primarily affect the very first few interactions end users have with TypeScript, which we should address via tooling. How this works is closely related to where the type definition files are generated during publication, and so will likely need to be solved in conjunction with that issue.
 
+- **What should the final design for template-aware type checking be?** [Glint][glint] has a number of decisions which make good sense and indeed are necessary for template-aware type checking given both the design constraints of the Octane era and its own experimental status. However, we should nail these down before it becomes an officially-recommended tool!
+
+[glint]: https://github.com/typed-ember/glint
+
 
 #### Recommendations