Update CI & engine support to Node 18

Node 14 seems to have issues with modern 'npm ci' and has been EOL for a
long time. Time to update to modern releases.

Author: pimterry

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [14.x, 16.x, 18.x, 20.x, v20.8.0, '*']
+        node-version: [18.x, 20.x, v20.11.1, '*']
 
     steps:
       - uses: actions/checkout@v3

package.json

@@ -50,6 +50,9 @@
     "url": "https://github.com/httptoolkit/brotli-wasm/issues"
   },
   "homepage": "https://github.com/httptoolkit/brotli-wasm#readme",
+  "engines": {
+    "node": ">=v18.0.0"
+  },
   "devDependencies": {
     "@peculiar/webcrypto": "^1.4.0",
     "@types/atob": "^2.1.2",