Add support of multi-columns descriptions

[Koc]

Now we can use multi-columns descriptions thankful to markdown-it-container plugin

::::: columns
:::: column-double
first column has double relative width (ie 2/3 of total width) 
::::
:::: column-single
second column has single relative width (ie 1/3 of total width)
::::
:::::

🔍 Preview

[susnux]

I am not sure about this, I do not see a good use case and will make thing more complex.
I would probably stick with CommonMark to keep it simple.

Opinions @jancborchardt @Chartman123 ?

[Chartman123]

Yeah same for me... another dependency for only a really small benefit.

[Koc]

for our use case It has sense for students quizzes, e.g. we have some image/schema on the left column and a question on the right column

[Koc]

Updates:

• properly handle columns on mobile
• added more real-life example in PR description
• fixed pipeline

[Chartman123]

@Koc thanks for the updated description with the preview... How would this work together with your other PR to implement Text as a Markdown editor? As far as I could see Text doesn't support multi-columns.

[Koc]

@Chartman123 I've plan to close #2164 because it requires much more work than I expected for adding images support. So there are no any conflicts with this 2 PRs anymore 😃