Add plugin implements test

Author: jmattheis

go.mod

@@ -3,4 +3,5 @@ module github.com/gotify/plugin-template
 require (
 	github.com/gin-gonic/gin v1.3.0
 	github.com/gotify/plugin-api v1.0.0
+	github.com/stretchr/testify v1.3.0
 )

plugin_test.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/gotify/plugin-api"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAPICompatibility(t *testing.T) {
+	assert.Implements(t, (*plugin.Plugin)(nil), new(MyPlugin))
+	// Add other interfaces you intend to implement here
+}