Add pre-commit hook. (#15)

.editorconfig

@@ -2,4 +2,4 @@ root = true
 
 [*.py]
 indent_style = space
-indent_size = 4
+indent_size = 4

.pre-commit-config.yaml

@@ -0,0 +1,15 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v5.0.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-merge-conflict
+      - id: check-case-conflict
+
+ci:
+  autofix_commit_msg: "[pre-commit.ci] Auto fixes from pre-commit.com hooks."
+  autofix_prs: true
+  autoupdate_commit_msg: "[pre-commit.ci] Pre-commit autoupdate."
+  autoupdate_schedule: quarterly
+  submodules: false