Add a bunch of test files.

To test some of the hooks with pre-commit try-repo.

test_files/docker-compose.yml

+---
+version: '3.5'
+services:
+  httpd:
+    image: docker.io/library/httpd:2.4-alpine

test_files/main.tf

+terraform {}

test_files/playbook.yml

+---
+- hosts: all
+  tasks:
+    - name: Debug
+      ansible.builtin.debug:
+        var: ansible_hostname

test_files/script.sh

+#!/bin/sh
+set -eu
+
+exit 0