Add reorder-python-import pre-commit hook

Also updated README.md

Change-Id: I118309c61f4d00e8508d6b888c606995490fba39
Signed-off-by: Diego Russo <diego.russo@arm.com>
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0695eff..d97d19f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,5 +1,10 @@
 exclude: '^ethosu/vela/(tflite|ethos_u55_regs)/'
 repos:
+- repo: https://github.com/asottile/reorder_python_imports
+  rev: v2.2.0
+  hooks:
+  - id: reorder-python-imports
+
 - repo: https://github.com/ambv/black
   rev: stable
   hooks: