wordpreass plugin should I need to licensing it under GPL?

Hi!
I’ve created a wordpress plugin and now ready to upload on codecanyon. Ive seen the general file preparation guidelines. But I’ve want to knoe some more things.

Should I need to licensing it under GPL?

Should I need to make a license folder and add GPL.txt and README_License.txt this two license file?

Any help will be appreciated. Thanks in advaned.