feat: add "PR: awaiting doc" label if doc changed
diff --git a/index.js b/index.js
index 212df55..71e158e 100644
--- a/index.js
+++ b/index.js
@@ -91,14 +91,24 @@
     app.on(['pull_request.opened'], async context => {
         // const auth = context.payload.pull_request.author_association;
         const isCore = isCoreCommitter(context.payload.pull_request.user.login);
-        const comment = context.github.issues.createComment(context.issue({
-            body: isCore ? text.PR_OPENED_BY_COMMITTER : text.PR_OPENED
-        }));
+        let commentText = isCore
+            ? text.PR_OPENED_BY_COMMITTER
+            : text.PR_OPENED;
 
         const labelList = ['PR: awaiting review'];
         if (isCore) {
             labelList.push('PR: author is committer');
         }
+        const content = context.payload.pull_request.body;
+        if (content && content.indexOf('[-] The API has been changed.') > -1) {
+            labelList.push('PR: awaiting doc');
+            commentText += '\n\n' + text.PR_AWAITING_DOC;
+        }
+
+        const comment = context.github.issues.createComment(context.issue({
+            body: commentText
+        }));
+
         const addLabel = context.github.issues.addLabels(context.issue({
             labels: labelList
         }));
@@ -106,6 +116,18 @@
         return Promise.all([comment, addLabel]);
     });
 
+    app.on(['pull_request.edited'], async context => {
+        const content = context.payload.pull_request.body;
+        if (content && content.indexOf('[-] The API has been changed.') > -1) {
+            return context.github.issues.addLabels(context.issue({
+                labels: ['PR: awaiting doc']
+            }));
+        }
+        else {
+            return getRemoveLabel(context, 'PR: awaiting doc');
+        }
+    });
+
     app.on(['pull_request.synchronize'], async context => {
         const addLabel = context.github.issues.addLabels(context.issue({
             labels: ['PR: awaiting review']
diff --git a/src/text.js b/src/text.js
index 9d13778..8f0764b 100644
--- a/src/text.js
+++ b/src/text.js
@@ -54,6 +54,9 @@
 
 The pull request is marked to be \`PR: author is committer\` because you are a committer of this project.`;
 
+const PR_AWAITING_DOC = `Document changes are required in this PR. Please also make a PR to [apache/incubator-echarts-doc](https://github.com/apache/incubator-echarts-doc) for document changes. When the doc PR is merged, the maintainers will remove the \`PR: awaiting doc\` label.
+`;
+
 const PR_MERGED =
     `Congratulations! Your PR has been merged. Thanks for your contribution! 👍`;
 
@@ -86,6 +89,7 @@
     PR_MERGED,
     PR_OPENED_BY_COMMITTER,
     PR_NOT_MERGED,
+    PR_AWAITING_DOC,
     ISSUE_TAGGED_WAITING_AUTHOR,
     ISSUE_TAGGED_EASY,
     ISSUE_TAGGED_PRIORITY_HIGH