Update Stylelint to version 16

[bedrich-schindler]

Update Stylelint to version 16

[adamkudrna]

⚠️ Caution! Reportedly, Stylelint has dropped some stylistic rules like line length or indentation. Options to fill the gap:

1. use Prettier
2. use a plugin

1. puts our coding style slightly out of our control, so 2) seems to be a better option.

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Thanks to @crishpeen for raising it up! ❤

[mbohal]

On video call we agreed, that we do not want to use Prettier, we do not think it is a good tool.

[mbohal]

Version 16 was released: https://github.com/stylelint/stylelint/releases/tag/16.0.0

[adamkudrna]

https://stylelint.io/migration-guide/to-15/