fix few issues with readme and add .gitignore

[antonydevanchi]

I hereby agree to the terms of the CLA available at: https://yandex.ru/legal/cla/?lang=ru

[antonydevanchi]

@dmitko помёржите, плез, а то у вас целый кусок документации поломан.

[corvus-migratorius]

@antonydevanchi Judging by the diff, virtually the only thing changed in README is backticks and a few newlines... 🤔

Though I agree that parts of the documentation are broken (e.g. where they show how to access issue attachments).