### Description
Add Rulemak Cyrillic layout, as found in
23fec5367a/symbols/ru (L722).
It's primarily designed for Russian, but can also be used for Ukrainian,
Serbian, Bulgarian, Belarusian and Macedonian, thanks to its layer 3-4
symbols.
### Checks
- [ ] Adding quotes?
- [ ] Make sure to include translations for the quotes in the
description (or another comment) so we can verify their content.
- [ ] Adding a language?
- Make sure to follow the [languages
documentation](https://github.com/monkeytypegame/monkeytype/blob/master/docs/LANGUAGES.md)
- [ ] Add language to `packages/schemas/src/languages.ts`
- [ ] Add language to exactly one group in
`frontend/src/ts/constants/languages.ts`
- [ ] Add language json file to `frontend/static/languages`
- [ ] Adding a theme?
- Make sure to follow the [themes
documentation](https://github.com/monkeytypegame/monkeytype/blob/master/docs/THEMES.md)
- [ ] Add theme to `packages/schemas/src/themes.ts`
- [ ] Add theme to `frontend/src/ts/constants/themes.ts`
- [ ] Add theme css file to `frontend/static/themes`
- [ ] Add some screenshot of the theme, especially with different test
settings (colorful, flip colors) to your pull request
- [x] Adding a layout?
- [x] Make sure to follow the [layouts
documentation](https://github.com/monkeytypegame/monkeytype/blob/master/docs/LAYOUTS.md)
- [x] Add layout to `packages/schemas/src/layouts.ts`
- [x] Add layout json file to `frontend/static/layouts`
- [ ] Adding a font?
- Make sure to follow the [themes
documentation](https://github.com/monkeytypegame/monkeytype/blob/master/docs/FONTS.md)
- [ ] Add font file to `frontend/static/webfonts`
- [ ] Add font to `packages/schemas/src/fonts.ts`
- [ ] Add font to `frontend/src/ts/constants/fonts.ts`
- [ ] Check if any open issues are related to this PR; if so, be sure to
tag them below.
- [ ] Make sure the PR title follows the Conventional Commits standard.
(https://www.conventionalcommits.org for more info)
- [ ] Make sure to include your GitHub username prefixed with @ inside
parentheses at the end of the PR title.
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