Add Renovate configuration files for automated dependency management

- Created .renovaterc for Renovate settings, including package rules for digest updates.
- Added renovate.config.cjs to define the Renovate bot's GitHub endpoint and author.
- Introduced a Gitea workflow in .gitea/workflows/renovate.yml to schedule daily runs of Renovate.

renovate.config.cjs

@@ -0,0 +1,6 @@
+module.exports = {
+	endpoint: "https://code.popov.link",
+	gitAuthor: "renovate[bot] <renovatebot@noreply.localhost>",
+	optimizeForDisabled: true,
+	platform: "gitea",
+};