Setup node 18 for testing matrix (#119)

diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 419f558..5442bd6 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -29,7 +29,7 @@
     timeout-minutes: 30
     strategy:
       matrix:
-        node-version: [ 10, 12, 14, 16 ]
+        node-version: [ 10, 12, 14, 16, 18 ]
     steps:
       - uses: actions/checkout@v2
         with:
diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index b2234d3..3295e1b 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -29,7 +29,7 @@
     timeout-minutes: 30
     strategy:
       matrix:
-        node-version: [ 10, 12, 14, 15 ]
+        node-version: [ 10, 12, 14, 16, 18 ]
     env:
       SW_NODE_VERSION: ${{ matrix.node-version }}
     steps: