add missing npm install command to docs flow

.github/workflows/generate_api_pages.yml

@@ -24,6 +24,9 @@ jobs:
       - name: Install swagger-codegen
         run: brew install swagger-codegen
 
+      - name: Npm install
+        run: npm install
+
       - name: Generate api pages for netbird main openapi definition
         run: |
           swagger-codegen generate -i https://raw.githubusercontent.com/netbirdio/netbird/v${{ steps.semver_parser.outputs.fullversion }}/management/server/http/api/openapi.yml -l openapi -o generator/openapi