implement draft/webpush (#2205)

vendor/github.com/ergochat/webpush-go/v2/README.md

@@ -0,0 +1,65 @@
+# webpush-go
+
+[![GoDoc](https://godoc.org/github.com/ergochat/webpush-go?status.svg)](https://godoc.org/github.com/ergochat/webpush-go)
+
+Web Push API Encryption with VAPID support.
+
+This library is a fork of [SherClockHolmes/webpush-go](https://github.com/SherClockHolmes/webpush-go).
+
+```bash
+go get -u github.com/ergochat/webpush-go/v2
+```
+
+## Example
+
+For a full example, refer to the code in the [example](example/) directory.
+
+```go
+package main
+
+import (
+	"encoding/json"
+
+	webpush "github.com/ergochat/webpush-go/v2"
+)
+
+func main() {
+	// Decode subscription
+	s := &webpush.Subscription{}
+	json.Unmarshal([]byte("<YOUR_SUBSCRIPTION>"), s)
+	vapidKeys := new(webpush.VAPIDKeys)
+	json.Unmarshal([]byte("<YOUR_VAPID_KEYS">), vapidKeys)
+
+	// Send Notification
+	resp, err := webpush.SendNotification([]byte("Test"), s, &webpush.Options{
+		Subscriber:      "example@example.com",
+		VAPIDKeys:       vapidKeys,
+		TTL:             3600, // seconds
+	})
+	if err != nil {
+		// TODO: Handle error
+	}
+	defer resp.Body.Close()
+}
+```
+
+### Generating VAPID Keys
+
+Use the helper method `GenerateVAPIDKeys` to generate the VAPID key pair.
+
+```golang
+vapidKeys, err := webpush.GenerateVAPIDKeys()
+if err != nil {
+	// TODO: Handle error
+}
+```
+
+## Development
+
+1. Install [Go 1.20+](https://golang.org/)
+2. `go mod vendor`
+3. `go test`
+
+#### For other language implementations visit:
+
+[WebPush Libs](https://github.com/web-push-libs)