Add output folder to gitignore
Add output folder to gitignore

Add output folder to gitignore since the files in this folder are generated by Pelican as mentioned in issue #18
Python-Monthly/pythonmonthly.github.io,Python-Monthly/pythonmonthly.github.io,Python-Monthly/pythonmonthly.github.io,Python-Monthly/pythonmonthly.github.io,Python-Monthly/Python-Monthly-Website,Python-Monthly/Python-Monthly-Website,Python-Monthly/Python-Monthly-Website,Python-Monthly/Python-Monthly-Website