add devlog/log example to readme

Author: hermannm

README.md

@@ -11,39 +11,39 @@ Run `go get hermannm.dev/devlog` to add it to your project!
 output for `slog`'s logging functions. It can be configured as follows:
 
 ```go
-logger := slog.New(devlog.NewHandler(os.Stdout, nil))
-slog.SetDefault(logger)
+logHandler := devlog.NewHandler(os.Stdout, nil)
+slog.SetDefault(slog.New(logHandler))
 ```
 
 Logging with `slog` will now use this handler:
 
 ```go
-slog.Warn("No value found for 'PORT' in env, defaulting to 8000")
-slog.Info("Server started", slog.Int("port", 8000), slog.String("environment", "DEV"))
+slog.Warn("no value found for 'PORT' in env, defaulting to 8000")
+slog.Info("server started", slog.Int("port", 8000), slog.String("environment", "DEV"))
 slog.Error(
-	"Database query failed",
+	"database query failed",
 	slog.Group("dbError", slog.Int("code", 60), slog.String("message", "UNKNOWN_TABLE")),
 )
 ```
 
 ...giving the following output (using a gruvbox terminal color scheme):
 
-![Screenshot of 3 log messages in a terminal](https://github.com/hermannm/devlog/blob/assets/devlog-example-output.png?raw=true)
+![Screenshot of log messages in a terminal](https://github.com/hermannm/devlog/blob/ac14f0dc1823316c983fb9cef6f1cf73a0bbb923/devlog-example-output.png?raw=true)
 
 This output is meant to be easily read by a developer working locally. However, you may want a more
 structured format for production, such as JSON, to make log analysis easier. You can get both by
 conditionally choosing the log handler for your application, e.g.:
 
 ```go
-var handler slog.Handler
+var logHandler slog.Handler
 switch os.Getenv("ENVIRONMENT") {
 case "PROD":
-	handler = slog.NewJSONHandler(os.Stdout, nil)
+	logHandler = slog.NewJSONHandler(os.Stdout, nil)
 case "DEV":
-	handler = devlog.NewHandler(os.Stdout, nil)
+	logHandler = devlog.NewHandler(os.Stdout, nil)
 }
 
-slog.SetDefault(slog.New(handler))
+slog.SetDefault(slog.New(logHandler))
 ```
 
 ## devlog/log
@@ -52,6 +52,34 @@ To complement `devlog`'s output handling, the
 [`devlog/log`](https://pkg.go.dev/hermannm.dev/devlog/log) subpackage provides input handling. It is
 a thin wrapper over the `slog` package, with utility functions for log message formatting.
 
+Example using `devlog` and `devlog/log` together:
+
+```go
+import (
+	"errors"
+	"log/slog"
+	"os"
+
+	"hermannm.dev/devlog"
+	"hermannm.dev/devlog/log"
+)
+
+func main() {
+	logHandler := devlog.NewHandler(os.Stdout, &devlog.Options{Level: slog.LevelDebug})
+	slog.SetDefault(slog.New(logHandler))
+
+	err := errors.New("invalid username")
+	log.ErrorCause(err, "failed to create user") // Uses slog.Default()
+
+	userJSON := map[string]any{"id": 1, "username": "hermannm"}
+	log.DebugJSON(userJSON, "user")
+}
+```
+
+This gives the following output:
+
+![Screenshot of log messages in a terminal](https://github.com/hermannm/devlog/blob/ac14f0dc1823316c983fb9cef6f1cf73a0bbb923/devlog-example-output-2.png?raw=true)
+
 ## Credits
 
 - [Jonathan Amsterdam](https://github.com/jba) for his fantastic