Translate into Japanese.

[feliz-me]

I am Japanese, and I use BDP on a daily basis.
Despite the fact that BDP has a certain number of Japanese users, there is no translation into Japanese.
So, I am trying to translate it into Japanese.

I have read translate.md and understand how to commit.
Is there any problem in doing this translation?
If no, I'll commit and pull request.

[SanjaySunil]

I'm currently not using any translations for the control panel (BetterDiscordPanel.cmd) as I need to make some changes to it when I have time.

However, it would be greatly appreciated if translations can be made for the actual BDP web panel.