Use node 14 to build docs (#373)

Author: kurkle

.github/workflows/documentation.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/checkout@v1
       - uses: actions/setup-node@v1
         with:
-          node-version: '12.x'
+          node-version: '14.x'
       - name: Test Build
         run: |
           npm ci
@@ -26,7 +26,7 @@ jobs:
       - uses: actions/checkout@v1
       - uses: actions/setup-node@v1
         with:
-          node-version: '12.x'
+          node-version: '14.x'
       - name: Build
         run: |
           npm ci