fix: use `[x]` but not `[-]` to check if checkbox exists and is checked.
diff --git a/index.js b/index.js
index 71e158e..ed40ec3 100644
--- a/index.js
+++ b/index.js
@@ -100,7 +100,7 @@
             labelList.push('PR: author is committer');
         }
         const content = context.payload.pull_request.body;
-        if (content && content.indexOf('[-] The API has been changed.') > -1) {
+        if (content && content.indexOf('[x] The API has been changed.') > -1) {
             labelList.push('PR: awaiting doc');
             commentText += '\n\n' + text.PR_AWAITING_DOC;
         }
@@ -118,7 +118,7 @@
 
     app.on(['pull_request.edited'], async context => {
         const content = context.payload.pull_request.body;
-        if (content && content.indexOf('[-] The API has been changed.') > -1) {
+        if (content && content.indexOf('[x] The API has been changed.') > -1) {
             return context.github.issues.addLabels(context.issue({
                 labels: ['PR: awaiting doc']
             }));