chore: add info re: always updating images (#2635)

docs/templates.md

@@ -162,6 +162,28 @@ resource "docker_container" "workspace" {
 }
 ```
 
+#### Using updated images when rebuilding a workspace
+
+To ensure that Coder uses an updated image when rebuilding a workspace, we
+suggest that admins update the tag in the template (e.g., `my-image:v0.4.2` ->
+`my-image:v0.4.3`) or digest (`my-image@sha256:[digest]` ->
+`my-image@sha256:[new_digest]`).
+
+Alternatively, if you're willing to wait for longer start times from Coder, you
+can set the `imagePullPolicy` to `Always` in your Terraform template; when set,
+Coder will check `image:tag` on every build and update if necessary:
+
+```tf
+resource "kubernetes_pod" "podName" {
+    spec {
+        container {
+            image_pull_policy = "Always"
+        }
+    }
+}
+```
+
+
 #### Delete workspaces
 
 When a workspace is deleted, the Coder server essentially runs a