docs: improve description of enable_jekyll=disable_nojekyll (see #130)

[Cito]

This assumes enable_jekyll is implemented as (the preferred) alias for disable_nojekyll (see #130).

[peaceiris]

Thank you!

After merging the implementation of enable_jekyll by me, this pull request will be merged into the master. I will release it as v3.5.0 and update the v3 tag.

[peaceiris]

Can this description confuse users who use Jekyll on Docker? Actually, they do not need enable_jekyll: true. Their pages process may be slow without .nojekyll.

[peaceiris]

The current description mentions .nojekyll file, not the GitHub Pages built-in Jekyll.

I came to think that we do not have to refer to the role of the .nojekyll file...

[peaceiris]

How about disable_adding_nojekyll_file instead of enable_jekyll?

[Cito]

How about disable_adding_nojekyll_file instead of enable_jekyll?

That's clearer than disable_nokeyll, but longer and clumsy, and I still I don't like the double negation that forces you to "think around the corner" as we say in German.

When deploying, users only care about whether Jekyll processing is enabled or not, They don't actually care what semaphore mechanism is used to achieve this (the .nojekyill file). That's why I mentioned it only in the second paragraph for those to understand the exact details.

[peaceiris]

Thanks to your great work, the description became more clear! LGTM.

After merging the implementation of enable_jekyll by me, this pull request will be merged into the master. I will release it as v3.5.0 and update the v3 tag.