Add arrtrix Matrix bridge service and package scaffolding

packages/arrtrix/pkg/connector/config.go

@@ -0,0 +1,18 @@
+package connector
+
+import (
+	_ "embed"
+
+	up "go.mau.fi/util/configupgrade"
+)
+
+//go:embed example-config.yaml
+var ExampleConfig string
+
+type Config struct{}
+
+func upgradeConfig(helper up.Helper) {}
+
+func (s *ArrtrixConnector) GetConfig() (string, any, up.Upgrader) {
+	return ExampleConfig, &s.Config, up.SimpleUpgrader(upgradeConfig)
+}