4-space indent selected text in description

https://ombulabs.atlassian.net/browse/DT-263

**Branch/Commit:**

Main branch

**Describe the feature:**

> **As a developer**
> **I select some lines from the description**
> **And then I click a button**
> **And I see the selected lines indented with 4 leading white spaces so it's formatted as a block**

**Problem:**

Currently, if we want to add code, we have two methods:
- triple backticks around the code (which is not always reliable and adds a color to the code)
- 4-spaces indentation (which is pretty annoying to adjust the indentation once the code is in the desription box or you have to update the indentation before copying the code)

**I will abide by the [code of conduct](CODE_OF_CONDUCT.md)**

Start from the description box in the main branch and locate the control that acts on selected lines. Verify how selection and indentation are currently handled, then confirm that clicking the button adds four leading spaces to the selected lines and that the resulting text is formatted as a block.

Written by the indexing model from the issue text.