add dummy getPodcasts view

fixes #98

server/ctrlsubsonic/handlers_unimplemented.go

@@ -0,0 +1,15 @@
+package ctrlsubsonic
+
+import (
+	"net/http"
+
+	"go.senan.xyz/gonic/server/ctrlsubsonic/spec"
+)
+
+func (c *Controller) ServeGetPodcasts(r *http.Request) *spec.Response {
+	sub := spec.NewResponse()
+	sub.Podcasts = &spec.Podcasts{
+		List: []struct{}{},
+	}
+	return sub
+}