imagestorage: fix templating of public_url option for webdav (#74885)

* spelling in error message

* imguploader: fix template for webdav url

Since a few years ago, when loading the config file, the  template gets replaced in the expanding
env var phase (see ##25075) and introduced a bug in the webdav public_url config option. This commit
changes the template syntax to be {{file}}. This doesn't get expanded and removed when the config file
is loaded.

* devenv: add a block for a WebDAV server

* Adding alerting as codeowners for webdav

---------

Co-authored-by: Timur Olzhabayev <timur.olzhabayev@grafana.com>

pkg/setting/expanders.go

@@ -57,7 +57,7 @@ func expandConfig(file *ini.File) error {
 	for _, expander := range expanders {
 		err := expander.expander.SetupExpander(file)
 		if err != nil {
-			return fmt.Errorf("got error during initilazation of expander '%s': %w", expander.name, err)
+			return fmt.Errorf("got error during initialization of expander '%s': %w", expander.name, err)
 		}
 
 		for _, section := range file.Sections() {