chore(ci): add renovate.json

The version of Ruby is pinned to at most `3.2.x`.

Signed-off-by: JP-Ellis <josh@jpellis.me>

.github/renovate.json

@@ -0,0 +1,14 @@
+{
+	"$schema": "https://docs.renovatebot.com/renovate-schema.json",
+	"extends": ["config:best-practices"],
+	"prHourlyLimit": 0,
+	"prConcurrentLimit": 0,
+	"packageRules": [
+		{
+			"groupName": "Ruby 3.2",
+			"groupSlug": "ruby-3.2",
+			"matchPackageNames": ["ruby"],
+			"allowedVersions": "<=3.2"
+		}
+	]
+}