Add option to change the language

[Hareon]

I am translating the app to brazilian portuguese, and an option to select the language would be interesting instead of simply changing it in the installation folder.

Here the link to my translation https://www.crowdin.com/project/traduo-de-extenses-phpbb/pt-BR#/Ultimate%20Points%20Extension

For now I've just started, but as I use it and like it, I'll translate more.

Please continue developing this excellent extension!

[Hareon]

As I was learning how to use phpBB, I didn't see that it was enough to create a folder in the Language folder to translate. Now that I understand this, you can disregard this issue. But I will continue translating the extension.