Add doc about manual deployment. (#186)

diff --git a/.github/workflows/deploy.yaml b/.github/workflows/deploy.yaml
index 1ca179c..dea734b 100644
--- a/.github/workflows/deploy.yaml
+++ b/.github/workflows/deploy.yaml
@@ -13,11 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-name: deploy site
+name: Build site
 
 on:
+  pull_request:
   push:
-    branches: 
+    branches:
       - master
 
 jobs:
@@ -33,7 +34,7 @@
           tar xvf hugo_extended_0.74.3_Linux-64bit.tar.gz
           sudo mv hugo /usr/bin/
           npm install -D --save postcss-cli
-          npm install -D --save autoprefixer
+          npm install -D --save autoprefixer	
           npm install -D --save postcss
           npm i
 
diff --git a/README.md b/README.md
index 0bfea92..b738cdf 100755
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@
 
 1. Install hugo
 1. Pull this repo into your local environment, and run `hugo server`  at the root folder, you can see the site preview from http://localhost:1313
-1. To generate the static website, run `hugo`
+1. To generate the static website, run `hugo`. According to ASF policy, the deployment has to be manually done by a committer. Use the generated `public` folder to update the `asf-site` branch, and push the updates to the upstream.
 
 ## Contributing
 
@@ -93,4 +93,3 @@
 ### Images
 
 The images within the blogs, events and 中文博客 should keep at the same folder as the blog file, and you should reference that with the relative path.
-