Bump minimum supported Node.js version to v18

The LTS releases for v12 and v14 are already end of life and the v16 is
end of life in under two months from now on.  Bump supported version up
to v18 as it does not make sense to continue to support EOL releases.
Even if we wanted to keep supporting them, our dependencies will not.

Note that Node.js v18 is currently not avaliable via the NodeSource PPA
on Ubuntu 19.10 and below or Debian 9 and below.

.github/workflows/node.js.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 16.x]
+        node-version: [18.x, 20.x]
         # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
 
     steps:
@@ -29,13 +29,13 @@ jobs:
     - run: node packages/lib/build_mod --source-dir packages/host/lua/clusterio_lib --output-dir temp/test/mods
     - run: wget -q -O temp/test/mods/subspace_storage_1.99.8.zip -L https://github.com/clusterio/subspace_storage/releases/download/1.99.6/subspace_storage_1.99.8.zip
     - name: Run tests
-      if: ${{ matrix.node-version != '12.x' }}
+      if: ${{ matrix.node-version != '18.x' }}
       run: pnpm test
     - name: Run coverage
-      if: ${{ matrix.node-version == '12.x' }}
+      if: ${{ matrix.node-version == '18.x' }}
       run: pnpm run ci-cover
     - name : Upload coverage to Codecov
-      if: ${{ matrix.node-version == '12.x' }}
+      if: ${{ matrix.node-version == '18.x' }}
       uses: codecov/codecov-action@v2
       with:
         files: ./coverage/lcov.info