Update node from 16 to 18

.github/workflows/frontend.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [16]
+        node-version: [18]
     steps:
       - name: Harden Runner
         uses: step-security/harden-runner@1f99358870fe1c846a3ccba386cc2b2246836776 # v2.2.1

Dockerfile

@@ -16,7 +16,7 @@ COPY docs/user_guide docs/user_guide
 RUN tox -e user-guide
 
 # Frontend build environment.
-FROM node:16 AS frontend_builder
+FROM node:18.15-bullseye-slim AS frontend_builder
 WORKDIR /app
 
 # Install app dependencies.

README.md

@@ -84,7 +84,7 @@ A rapid word collection tool. See the [User Guide](https://sillsdev.github.io/Th
    ```
 
 2. [Chocolatey][chocolatey]: (Windows only) a Windows package manager.
-3. [Node.js 16 (LTS)](https://nodejs.org/en/download/)
+3. [Node.js 18 (LTS)](https://nodejs.org/en/download/)
    - On Windows, if using [Chocolatey][chocolatey]: `choco install nodejs-lts`
    - On Ubuntu, follow
      [this guide](https://github.com/nodesource/distributions/blob/master/README.md#installation-instructions) using the

package.json

@@ -212,5 +212,8 @@
       "last 1 firefox version",
       "last 1 safari version"
     ]
+  },
+  "volta": {
+    "node": "18.15.0"
   }
 }