fix(ci): use extended hugo; install modules for tests

.woodpecker/.docs.yml

@@ -4,7 +4,7 @@ branches:
 
 pipeline:
   docs:
-    image: 'klakegg/hugo:alpine'
+    image: 'klakegg/hugo:ext-alpine'
     group: 'generate'
     commands:
       - apk add git

.woodpecker/.test.yml

@@ -8,6 +8,15 @@ branches:
 platform: ${PLATFORM}
 
 pipeline:
+  install-modules:
+    image: 'chewingbever/vlang:latest'
+    pull: true
+    commands:
+      - export VMODULES=$PWD/.vmodules
+      - 'cd src && v install'
+    when:
+      event: [pull_request]
+
   test:
     image: 'chewingbever/vlang:latest'
     pull: true