更改：疑修param为index以及新增统计标签下合并请求数量

db/migrate/20230223065106_add_some_columns_to_issue_upgrade.rb

@@ -0,0 +1,5 @@
+class AddSomeColumnsToIssueUpgrade < ActiveRecord::Migration[5.2]
+  def change
+    add_column :issue_tags, :pull_requests_count, :integer, default: 0
+  end
+end