feat(knex): initial knexjs migration

Co-authored-by: Philip Molares <philip.molares@udo.edu>
Signed-off-by: Erik Michelson <github@erik.michelson.eu>
Signed-off-by: Philip Molares <philip.molares@udo.edu>

backend/knexfile.ts

@@ -0,0 +1,21 @@
+/*
+ * SPDX-FileCopyrightText: 2025 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import type { Knex } from 'knex';
+
+/** This is used for the Knex CLI to create migrations during development */
+const config: { [key: string]: Knex.Config } = {
+  development: {
+    client: 'better-sqlite3',
+    connection: {
+      filename: './hedgedoc.sqlite',
+    },
+    migrations: {
+      directory: './src/database/migrations',
+    },
+  },
+};
+
+module.exports = config;