Add pre-commit integration (#556)

This PR introduces direct [pre-commit](https://pre-commit.com/)
compatibility.

Here is an example of how it can be integrated after it will be
integrated:
```
repos:
-   repo: https://github.com/sql-formatter-org/sql-formatter
    rev: ''
    hooks:
    -   id: sql-formatter
```

Right now you need to create a separate repository in order to be able
to integrate with `sql-formatter`.
Like this one: https://github.com/slyapustin/pre-commit-sql-formatter

.pre-commit-hooks.yaml

@@ -0,0 +1,6 @@
+-   id: sql-formatter
+    name: sql-formatter
+    description: "Reformat SQL files with sql-formatter"
+    entry: sql-formatter --fix
+    language: node
+    types: [sql]