chore(deps): pin node.js to 21.0.0 (#244)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [node](https://togithub.com/nodejs/node) | engines | pin | [`20 \|\|
21` -> `21.0.0`](https://renovatebot.com/diffs/npm/node/v21.0.0/v21.0.0)
|

Add the preset `:preserveSemverRanges` to your config if you don't want
to pin your dependencies.

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Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Johannes Andersen <jotoffen@gmail.com>

.nvmrc

@@ -1 +1 @@
-20.8.1
+21.0.0

package.json

@@ -11,7 +11,7 @@
     "format:check": "prettier --check \"**/*.{ts,tsx,js,md}\""
   },
   "engines": {
-    "node": "20 || 21",
+    "node": "21.0.0",
     "npm": "9 || 10"
   },
   "dependencies": {