Fix typos & wording in README + fix of book compilation errors

[dev99problems]

Description

This brings some typos adjustments and wording updates to README.md to make wording there a bit more formal
and a bit less authorish.

Also fixes 2 books generation errors:

• including non-existing contributors.txt file — original eng. book now is providing a link to it in contributors.asc, instead or including it, but the fun part — I couldn't find the contributors.txt file itself in eng. repo either, so just switching from including to link worked pretty well
• fixes the asciidoc formatting issue in book/06-github/3-maintaining.asc section

[dev99problems]

@burlakvo , @hedrok folks, if you'll find time to go through and provide a feedback — I'd be thankful

[burlakvo]

@dev99problems, thanks for contributing!

There is one small notice regarding contributors.txt and in other files, I could suggest rewording "проект" into "проєкт"

I haven't the ability to approve PRs, only commenting =)

[burlakvo]

It's generated on the go by Rakefile, so there is no need for such changes

[dev99problems]

Thanks for mentioning this!
I couldn't make bundle install land all the deps normally on [email protected], for some reason there's a problem with
[email protected] gem on my MacOS setup, so I wasn't able to run bundle exec rake normally.

Reverting this one

[dev99problems]

Reverted

[dev99problems]

@dev99problems, thanks for contributing!

There is one small notice regarding contributors.txt and in other files, I could suggest rewording "проект" into "проєкт"

I haven't the ability to approve PRs, only commenting =)

Was thinking about проєкт as well, because seems like since 2019 it is the proper & official spelling.
Will update in README.md

[dev99problems]

@hedrok якщо буде змога, могли б подивитись ці зміни?

[hedrok]

Дякую, залив.