Enhancements in /juna command

[CxrlosKenobi]

To improve

As said in the #7 comment, there are possible improvements that were left open to the community to be able to carry them out and collaborate with the project. So far:

• Modify the get_menu() function in order to pass args of a given day, and get the lunch menu of that day!

example: /juna ayer which would return yesterday's menu, and so on with nearby days

I encourage the team to close this issue via pull request 👁️ 😄 !
@fcocea @albfr @nwroot @montti