Update BG translation for PD mode options

[ia]

• Please check if the PR fulfills these requirements

• The changes have been tested locally
• There are no breaking changes

• What kind of change does this PR introduce?
  Update RU translation for PD mode options.

• What is the current behavior?
  Description for PD mode and its modes are not translated.

• What is the new behavior (if this is a feature change)?
  Translated description for PD mode and for its modes.

• Other information:
  Before submitting the patch I did make a set of custom builds to find the most adequate "adoption" to make it fit and to have it clear (as much as possible) at the same time for an average user.

Also, I tried to get some additional information about options and what exactly they do here in a form of code review comment. But I think I figured it out after all, more or less.

P.S. As always, I understand we all busy with our lives as well. But I still determine to keep dedicating some of my time to this project when I can with everything I can.

[Ralim]

The code review comment never posted? Did you make sure to submit it from pending?

[ia]

The code review comment never posted?

Oh... wait, indeed! It has "Label: Pending". I thought what it means is "now it's waiting for reply"! Oops... 😳

Did you make sure to submit it from pending?

I feel myself ashamed asking this but... how should I do that exactly? I don't see any "publish"/"submit" code comment button in that PR form. Is it possible that it's because that pull-request (#1917) is merged & closed already? Just curious.

UPD: Aaaaaa... I got this! Ufff, wow, now I see! My bad indeed. Will publish it in a couple minutes. Sorry.

[ia]

Status update: just don't merge this yet, please. I will prepare a little update in a day or so.

[ia]

Status update: just don't merge this yet, please. I will prepare a little update in a day or so.

Done. Now it should sound more clear.