Add count for current users online

[lcezermf]

Why is this change being made?

Adds #79

How is this being accomplished?

It adds a counter based on the amount of users accessing the website. This was done using Presence from Phoenix to handle the whole behavior.

Every LV module on the mount will trigger the Presence and a component on the home page will render the proper value.

Testing

• Run the project
• Access the home page
• [ ] Must show the value of total online users
• Open a anon browser and access a new page
• [ ] It must update the value for the count

Take aways

• UI is not my strongest skill so any suggestion or commit would be helpful
• There is a couple of copy and paste code, I do not see as a problem now, but in future that can be improved

[lcezermf]

@danielbergholz all accepted, running locally it keeps working fine.

[danielbergholz]

Impressive work @lcezermf! Thanks for spending the time to implement such a cool feature 🔥

[lcezermf]

Close #79