ci: fix typedoc plugin install/build command (tauri-apps#1122)

Author: FabianLars

.github/workflows/update-docs.yml

@@ -54,8 +54,11 @@ jobs:
         run: git submodule update --remote
 
       - name: Build typedoc-plugin-markdown
-        working-directory: ./tauri-docs/packages/typedoc-plugin-markdown/packages/typedoc-plugin-markdown
-        run: yarn && yarn build
+        working-directory: ./tauri-docs/packages/typedoc-plugin-markdown
+        run: |
+          npm install
+          cd packages/typedoc-plugin-markdown/
+          yarn build
 
       - name: Prep for JS doc generation
         working-directory: ./tauri/tooling/api