docs: Implement incus_image_alias resource

Signed-off-by: Ruihua Wen <[email protected]>

Author: SpiffyEight77

docs/resources/image_alias.md

@@ -0,0 +1,33 @@
+# incus_image_alias
+
+Manages a locally-stored Incus image alias.
+
+## Example Usage
+
+```hcl
+resource "incus_image" "alpine" {
+  source_image = {
+    remote = "images"
+    name   = "alpine/edge"
+  }
+}
+
+resource "incus_image_alias" "alpine" {
+  alias       = "alpine"
+  description = "Alpine Edge"
+  fingerprint = incus_image.alpine.fingerprint
+}
+```
+
+## Argument Reference
+
+* `alias` - *Required* - An alias to assign to the image after pulling.
+
+* `description` - *Optional* - Description of the image alias.
+
+* `fingerprint` - *Required* - The unique hash fingperint of the image.
+
+* `project` - *Optional* - Name of the project where the image will be stored.
+
+* `remote` - *Optional* - The remote in which the resource will be created. If
+  not provided, the provider's default remote will be used.