Updated README to be useful.

README.md

@@ -2,3 +2,21 @@
 
 meager.io pre-commit hooks for Scala 3 development. Used to run `scalafmt` on
 commit.
+
+## Usage
+
+Create `.pre-commit-config.yaml` at the root of your repository:
+
+```yaml
+---
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.3.0
+    hooks:
+      - id: end-of-file-fixer
+      - id: trailing-whitespace
+  - repo: https://git.sr.ht/~eidolon/meager-pre-commit-scala
+    rev: v0.1.1
+    hooks:
+      - id: scalafmt
+```