Update README for clarity and add entity association support

Author: nakamura-to

README.md

@@ -1,14 +1,13 @@
 Doma
 ====
 
-Doma is a database access framework for Java.
-Doma has various strengths:
-
-- Verifies and generates source code **at compile time** using [annotation processing][apt].
-- Provides type-safe Criteria API.
-- Supports Kotlin.
-- Uses SQL templates, called "two-way SQL".
-- Has no dependence on other libraries.
+Doma is a database access framework for Java with several notable strengths:
+
+- It checks and generates source code at compile time using annotation processing.
+- It supports associations between entities.
+- It offers a type-safe Criteria API.
+- It includes SQL templates, known as “two-way SQL.”
+- It runs independently, without relying on any other libraries.
 
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