move v2 module to root of repo

Updates tailscale/corp#22748

Signed-off-by: Percy Wegmann <[email protected]>

Author: oxtoacart

README.md

@@ -0,0 +1,55 @@
+# tailscale.com/client/tailscale/v2
+
+[![Go Reference](https://pkg.go.dev/badge/tailscale.com/client/tailscale/v2.svg)](https://pkg.go.dev/tailscale.com/client/tailscale/v2)
+[![Github Actions](https://github.com/tailscale/tailscale-client-go-v2/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/tailscale/tailscale-client-go-v2/actions/workflows/ci.yml)
+
+The official client implementation for the [Tailscale](https://tailscale.com) HTTP API.
+For more details, please see [API documentation](https://tailscale.com/api).
+
+## Example (Using API Key)
+
+```go
+package main
+
+import (
+	"context"
+	"os"
+
+	"tailscale.com/client/tailscale/v2"
+)
+
+func main() {
+	client := &tailscale.Client{
+		Tailnet: os.Getenv("TAILSCALE_TAILNET"),
+		APIKey:  os.Getenv("TAILSCALE_API_KEY"),
+	}
+
+	devices, err := client.Devices().List(context.Background())
+}
+```
+
+## Example (Using OAuth)
+
+```go
+package main
+
+import (
+	"context"
+	"os"
+
+	"tailscale.com/client/tailscale/v2"
+)
+
+func main() {
+	client := &tailscale.Client{
+		Tailnet: os.Getenv("TAILSCALE_TAILNET"),
+		HTTP:    tailscale.OAuthConfig{
+			ClientID:     os.Getenv("TAILSCALE_OAUTH_CLIENT_ID"),
+			ClientSecret: os.Getenv("TAILSCALE_OAUTH_CLIENT_SECRET"),
+			Scopes:       []string{"all:write"},
+		}.HTTPClient(),
+	}
+	
+	devices, err := client.Devices().List(context.Background())
+}
+```