port generic Renovate options from gitea's renovate.json5 (#545)

Ports repo-agnostic options from gitea/gitea's `renovate.json5`:

- `default.json`: `minimumReleaseAge: "5 days"`, `configMigration: true`
- `go-deps.json`: `gomodUpdateImportPaths` postUpdateOption + immediate Go toolchain bumps (opt-in preset, no-op without `go.mod`)
- `npm-deps.json`: `pnpmDedupe` postUpdateOption (no-op for non-pnpm repos)

Reviewed-on: https://gitea.com/gitea/renovate-config/pulls/545
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

default.json

@@ -1,6 +1,8 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": ["config:recommended","local>gitea/renovate-config:workflow-deps"],
+  "configMigration": true,
+  "minimumReleaseAge": "5 days",
   "semanticCommits": "enabled",
   "automergeStrategy": "auto",
   "platformAutomerge": false