ci: Add renovate config (#35)

Renovate is a popular tool in the JavaScript ecosystem that automates
dependency management and helps keep your project's dependencies up to
date. It is designed to work with package managers like npm, Yarn, and
others.

Renovate will open a PR when a package is updated, grouping them by the
rules defined in this PR.

Signed-off-by: Tyler Smalley <tyler@tailscale.com>

.github/renovate.json5

@@ -0,0 +1,35 @@
+{
+  $schema: 'https://docs.renovatebot.com/renovate-schema.json',
+  extends: ['config:base'],
+  enabledManagers: ['npm'],
+  baseBranches: ['main'],
+  prConcurrentLimit: 0,
+  rangeStrategy: 'bump',
+  prHourlyLimit: 0,
+  packageRules: [
+    {
+      groupName: 'react',
+      matchPackagePatterns: ['^react', '.*react$'],
+    },
+    {
+      groupName: 'eslint',
+      matchPackagePatterns: ['^eslint', '^@typescript-eslint'],
+    },
+    {
+      groupName: 'typescript',
+      matchPackagePatterns: ['^typescript', '^@typescript'],
+    },
+    {
+      groupName: 'tailwindcss',
+      matchPackagePatterns: ['^tailwindcss', '^@tailwindcss', '.*tailwindcss$'],
+    },
+    {
+      groupName: 'webpack',
+      matchPackagePatterns: ['^webpack', '-loader$'],
+    },
+    {
+      groupName: 'vscode',
+      matchPackagePatterns: ['^@vscode', '^@types/vscode', '^vscode'],
+    },
+  ],
+}