readme: minor refine

Author: wonderbeyond

README.md

@@ -1,16 +1,14 @@
 SQLAlchemy-Nested-Mutable
 =========================
 
-```shell
-pip install sqlalchemy-nested-mutable
-```
-
 An advanced SQLAlchemy column type factory that helps map compound Python types (e.g. `list`, `dict`, *Pydantic Model* and their hybrids) to database types (e.g. `ARRAY`, `JSONB`),
 And keep track of mutations in deeply nested data structures so that SQLAlchemy can emit proper *UPDATE* statements.
 
 SQLAlchemy-Nested-Mutable is highly inspired by SQLAlchemy-JSON<sup>[[0]](https://github.com/edelooff/sqlalchemy-json)</sup><sup>[[1]](https://variable-scope.com/posts/mutation-tracking-in-nested-json-structures-using-sqlalchemy)</sup>.
 However, it does not limit the mapped Python type to be `dict` or `list`.
 
+---
+
 ## Why this package?
 
 * By default, SQLAlchemy does not track in-place mutations for non-scalar data types
@@ -27,6 +25,12 @@ However, it does not limit the mapped Python type to be `dict` or `list`.
   which have strong schemas, with the db type be schema-less JSON.
 
 
+## Installation
+
+```shell
+pip install sqlalchemy-nested-mutable
+```
+
 ## Usage
 
 > NOTE the example below is first updated in `examples/user-addresses.py` and then updated here.