Set up pre-commit GitHub action and make README clearer

Author: Paulinakhew

.github/workflows/pre-commit.yml

@@ -0,0 +1,14 @@
+name: pre-commit
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+    - uses: pre-commit/[email protected]

README.md

@@ -196,8 +196,8 @@ next_url = page1.next_page_url
 page2 = shopify.Product.find(from_=next_url)
 ```
 
-## Development on this repo
-Install requirements and initialize [pre-commit](https://pre-commit.com/)
+## Set up pre-commit locally [OPTIONAL]
+[Pre-commit](https://pre-commit.com/) is set up as a GitHub action that runs on pull requests and pushes to the `master` branch. If you want to run pre-commit locally, install it and set up the git hook scripts
 ```shell
 pip install -r requirements.txt
 pre-commit install