Additional changes to README

[OlaPom]

Hello again!
This PR is for some additional changes I would like to suggest to your file. They are loosely inspired by technical writing style guides(such as Google Developer Style Guide or Microsoft Style Guide).

1. “Functionalities” - I focused on the language and rephrased some sentences that seemed too complicated (to me).
2. “Deployment” - this part is a real fun with all these different task descriptions :)
   I suppose that the file will change as your website develops, so I don’t want to suggest any revolution in the structure. However, I think that these writing tips would help keep it organised:

• numbered lists where possible
• bulleted lists for single-step tasks (as described here https://developers.google.com/style/procedures)
• using similar format - title (good to start with a verb), prerequisites, steps, result (nice template here https://docs.gitlab.com/ee/development/documentation/topic_types/task.html)

3. “Repository structure” - it says that it’s a list of the main files and folders. Does it mean you want to have only the most important files listed here or all of them? I can update the list with the names of the missing files, but you would have to add the descriptions.
4. Screenshots - if the interface changes frequently, then there is no point in adding screenshots, but I think it might be a good idea for the future.

Issue #106