docs: add readme text

README.md

@@ -1,2 +1,29 @@
-# sqlnull
-Go sql.Null-Types that implement Un/MarshalJSON
+# SQLNull
+
+A dead simple one stop solution to pass your database types directly to
+your JSON REST-API.
+
+This package provides wrapper types for all Null* types of the 
+[`database/sql`](https://pkg.go.dev/database/sql) which implement the 
+`Marshaler` and `Unmarshaler` interface of the 
+[`encoding/json`](https://pkg.go.dev/encoding/json) package.
+
+## Usage
+
+1. Get the package
+```bash
+go get github.com/gkits/nullsql@latest
+```
+
+2. Import the package
+```go
+import "github.com/gkits/nullsql"
+```
+
+3. Start coding...
+
+## Limitations
+
+Due to the internal implementation of the 
+[`encoding/json`](https://pkg.go.dev/encoding/json) package you can sadly
+not omit the fields with value `null` using the `omitempty` tag.