Add deprecation guide for RFC emberjs/rfcs#995

Author: NullVoxPopuli

content/ember/v5/deprecate-component-template-resolving.md

@@ -0,0 +1,80 @@
+---
+title: Component Template Resolving 
+until: 6.0.0
+since: 5.10.0
+---
+
+There are two types of paths to migrate off the old layouts 
+- use a currently supported multi-file layout (keeping separate `js`, `ts`, and `hbs` files)
+- migrate the component entirely to the latest component format, `gjs`, `gts`, (aka `<template>`)
+
+There are some tools to help with this:
+- [Classic to Colocation](https://github.com/ember-codemods/ember-component-template-colocation-migrator)
+- [Convert pods to Colocation](https://github.com/ijlee2/ember-codemod-pod-to-octane)
+- [Convert to `<template>`](https://github.com/IgnaceMaes/ember-codemod-template-tag)
+
+
+Specifically, these layouts are no longer supported:
+
+<table style="width:100%"><thead><tr><th>Classic</th><th>Pods</th></thead>
+<tbody><tr><td style="vertical-align:top; width:50%;">
+
+```
+{app,addon}/
+  components/
+    foo.js
+    namespace/
+      bar.js
+  templates/
+    components/
+      foo.hbs
+      namespace/
+        bar.hbs
+```
+
+</td><td style="vertical-align:top">
+
+```
+{app,addon}/
+  components/
+    foo/
+      component.js
+      template.hbs
+    namespace/
+      bar/
+        component.js
+        template.hbs
+```
+
+</td></tr></tbody>
+</table>
+
+
+The above example(s) can be migrated to:
+
+```
+{app,addon}/
+  components/
+    foo.js 
+    foo.hbs
+    namespace/
+      bar.js
+      bar.hbs
+```
+
+Or using `--component-structure=nested`
+
+```
+{app,addon}/
+  components/
+    foo/
+      index.js 
+      index.hbs
+    namespace/
+      bar/
+        index.js
+        index.hbs
+```
+
+Note, however, that classic components _importing_ the `layout` and setting it on an `@ember/component` will still work.
+The key thing being deprecated is the runtime resolution of templates, so if there is an import involved, there is no runtime resolution.