Add pre-commit

This is the configuration for pre-commit (https://pre-commit.com/#installation). It's an optional way of running pre-commit hooks. It won't force anyone to use it, but for those who do it offers a simple way to check linting before committing

Author: jonodrew

.pre-commit-config.yaml

@@ -0,0 +1,11 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v6.0.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+  - repo: https://github.com/mattlqx/pre-commit-ruby
+    rev: v1.3.6
+    hooks:
+      - id: rubocop
+      - id: rspec