docs(readme): add basic information and example

README.md

@@ -4,10 +4,75 @@
 
 <p align="center">
   <strong>
-    [WIP] Go package for object validation with a goal of simple and flexible.
+    Yet another Go struct/object validation package, with a focus on simplicity,
+    flexibility, and full control over validation logic.
   </strong>
 </p>
 
-## License
+---
+
+Add validation to any type, by simply implementing the `Validatable` interface:
+
+```go
+type Validatable interface {
+	Validate() error
+}
+```
+
+## Import
+
+```go
+import "github.com/romdo/go-validate"
+```
+
+## Example
+
+```go
+type Order struct {
+	Books []*Book `json:"books"`
+}
+
+type Book struct {
+	Title  string `json:"title"`
+	Author string `json:"author"`
+}
+
+func (s *Book) Validate() error {
+	var errs error
+	if s.Title == "" {
+		errs = validate.Append(errs, &validate.Error{
+			Field: "Title", Msg: "is required",
+		})
+	}
+
+	// Helper to perform the same kind of check as above for Title.
+	errs = validate.Append(errs, validate.RequireField("Author", s.Author))
+
+	return errs
+}
+
+func main() {
+	errs := validate.Validate(&Order{Books: []*Book{{Title: ""}}})
+
+	for _, err := range validate.Errors(errs) {
+		fmt.Println(err.Error())
+	}
+}
+```
+
+Above example produces the following output:
+
+```
+books.0.title: is required
+books.0.author: is required
+```
+
+## Documentation
+
+Please see the
+[Go Reference](https://pkg.go.dev/github.com/romdo/go-validate#section-documentation)
+for documentation and examples.
+
+## LICENSE
 
 [MIT](https://github.com/romdo/go-conventionalcommit/blob/main/LICENSE)