fix(version): change development version naming to avoid breaking some clients

Some Miniflux clients expect a specific version format.
For example, Flux News converts the string version to an integer.

Using `Development Version` will break some clients.

internal/template/functions.go

@@ -32,6 +32,7 @@ type funcMap struct {
 // Map returns a map of template functions that are compiled during template parsing.
 func (f *funcMap) Map() template.FuncMap {
 	return template.FuncMap{
+		"contains":         strings.Contains,
 		"startsWith":       strings.HasPrefix,
 		"formatFileSize":   formatFileSize,
 		"dict":             dict,