Improve README

Author: reda-alaoui

README.md

@@ -56,4 +56,68 @@ An annotation processor converting JSON schemas to java records.
    import com.cosium.json_schema_to_java_record_api.JsonSchemaConfiguration;
    import com.cosium.json_schema_to_java_record_api.JsonSchemaFileLocation;
    ```
-5. Compile to generate the java files
+5. Compile to generate the java files
+
+# Type mapping
+
+| JSON `type` | JSON `format` | JSON required | Java type               |
+|-------------|---------------|---------------|-------------------------|
+| object      |               |               | A java record           |
+| string      | date-time     |               | java.time.ZonedDateTime |
+| string      | uri           |               | java.net.URI            |
+| string      |               |               | java.lang.String        |
+| array       |               |               | java.util.List          |
+| number      |               | required      | double                  |
+| number      |               | non required  | java.lang.Double        |
+| integer     |               | required      | int                     |
+| integer     |               | non required  | java.lang.Integer       |
+| boolean     |               | required      | boolean                 |
+| boolean     |               | non required  | java.lang.Boolean       |
+| null        |               |               | java.lang.Void          |
+
+# JSON enum
+
+A schema having a non-null `enum` array will be converted to a java enum.
+
+# Java JSON binding
+
+Record components will be annotated with [Jackson annotations](https://github.com/FasterXML/jackson-annotations)
+
+# Nullability
+
+JSON schema [required](https://json-schema.org/understanding-json-schema/reference/object#required) is supported.
+By default, a property is considered as nullable. If a property is part of JSON schema [required](https://json-schema.org/understanding-json-schema/reference/object#required) array, it will be considered as non-nullable.
+
+## JSpecify
+
+If [JSpecify](https://jspecify.dev) nullness annotations (`@Nullable` and `@NonNull`) are part of the classpath,
+they will be used to annotate generated java record components.
+
+## Array
+
+# Builder
+
+## RecordBuilder
+
+If [RecordBuilder](https://github.com/Randgalt/record-builder) annotation `io.soabase.recordbuilder.core.RecordBuilder` 
+is part of the classpath, the former will be added to each generated java record.
+
+# $ref
+
+JSON schema [$ref](https://json-schema.org/understanding-json-schema/structuring#dollarref) is supported via the classpath "protocol."
+
+This allows you to have multiple JSON schema files referring to each other.
+
+All `$ref` values should start with `classpath:`, followed by the absolute path to the referred JSON file like this:
+```json
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "address",
+  "type": "object",
+  "properties": {
+    "country": {
+      "$ref": "classpath:/com/cosium/json_schema_to_java_record_tests/case1/country.json"
+    }
+  }
+}
+```