feat: Support templates with _template.json metadata (#1631)

Author: gadenbuie

CHANGELOG.md

@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * `shiny create` now supports a succinct format for specifying the GitHub repository via the `--github` flag, e.g. `--github posit-dev/py-shiny-templates`. You can now also use `--github` and `--template` together, in which case `--github` should point to a repository containing a directory matching the name provided in `--template`. (#1623)
 
+* `shiny create` now identifies templates in external repositories using a `_template.json` metadata file. This file should contain at an `"id"` and optionally a `"title"` and `"description"`. When `shiny create` is called with the `--github` flag but without a `--template` flag, it will offer a menu listing all available templates in the repository. (#1631)
+
 ### Other changes
 
 ### Bug fixes

shiny/_main.py

@@ -582,17 +582,21 @@ def create(
     dir: Optional[Path | str] = None,
     package_name: Optional[str] = None,
 ) -> None:
-    from ._main_create import use_template_github, use_template_internal
-
-    print(f"dir is {dir}")
+    from ._main_create import use_github_template, use_internal_template
 
     if dir is not None:
         dir = Path(dir)
 
     if github is not None:
-        use_template_github(github, template=template, mode=mode, dest_dir=dir)
+        use_github_template(
+            github,
+            template_name=template,
+            mode=mode,
+            dest_dir=dir,
+            package_name=package_name,
+        )
     else:
-        use_template_internal(template, mode, dir, package_name)
+        use_internal_template(template, mode, dir, package_name)
 
 
 @main.command(