Embed code snippets into README

[nifadyev]

Discussed in #340

Current contribution workflow contains a lot of duplication. For example, each translation duplicates code snippets and translates only comments.

Add support for embedded code Github Action
The goal is to store, test and analyze code snippets in one place, and reduce duplicity. It will probably break current interactive notebooks or CLI, their behavior should be checked. CI checks and validations, running snippets on various Python versions, automatic PR checks and so on.

UPD: It is important to note that Github code embedding is exclusive to Github. For example, it won't work in Jyputer notebook or static formats (epub, pdf). So called auto documentation should be considered as first option, some references:

• markdown-autodocs
• embedme
• markdown-embed-code - outdated github actions, might be forked and adopted to our needs
• markdown_code_embed - overcomplicated cli python script, might be forked and adopted to our needs