Change type of ESLint config and add ESLint Stylistic

[ansivgit]

📝 Describe the feature

To make it easier to switch to the latest version of ESLint in the future, we are changing the type of ESLint config to flat config and adding ESLint Stylistic to maintain quality control of the code style at the highest level.

ℹ️ Additional context

This task is subtask of #101

✅ Definition of Done (DoD):

• change type of ESLint config to flat config;
• add ESLint Stylistic to our packages;
• add rules for stricter code style;
• check that everything is working correctly.