fix(scripts): Run generate-migration-map after seed events (#17234)

* fix(scripts): Run generate-migration-map after seed events

* fix(only-once): Run 'ensure-env' on prelint

config/ensure-env.js

@@ -0,0 +1,25 @@
+var fs = require('fs');
+
+fs.access(
+  './server/rev-manifest.json',
+  function(err) {
+    if (err) {
+      console.log('\n\ncreating manifest\n\n');
+      return fs.writeFileSync('server/rev-manifest.json', '{}');
+    }
+    console.log('\n\nrev-manifest present\n\n');
+    return null;
+  }
+);
+
+fs.access(
+  './server/resources/pathMigration.json',
+  err => {
+    if (err) {
+      console.log('\n\ncreating pathMigration\n\n');
+      return fs.writeFileSync('server/resources/pathMigration.json', '{}');
+    }
+    console.log('\n\npathMigration present\n\n');
+    return null;
+  }
+);