chore: Update Node.js version to 20 in GitHub Actions workflows

Author: darkobas2

.github/workflows/build.yaml

@@ -20,7 +20,7 @@ jobs:
 
       - uses: actions/setup-node@v1
         with:
-          node-version: '18'
+          node-version: '20'
 
       - name: Build
         run: |

.github/workflows/gh-pages.yaml

@@ -17,7 +17,7 @@ jobs:
 
       - uses: actions/setup-node@v1
         with:
-          node-version: '18'
+          node-version: '20'
 
       - name: Build for gh-pages
         run: |