Upgrade ckeditor to version 34.2.0 and postcss to version 8

[alexander-schranz]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Fixed tickets	parts of #6343
Related issues/PRs	#
License	MIT
Documentation PR	sulu/sulu-docs#

What's in this PR?

Upgrade ckeditor to version 34.2.0.

Why?

Supporting the latest ckeditor features and plugins.

TODO

• Compatibility with PostCSS 8 madeleineostoja/postcss-hexrgba#31 all rgba($ do not longer work

[alexander-schranz]

https://ckeditor.com/docs/ckeditor5/latest/support/error-codes.html#error-editor-isreadonly-has-no-setter

[alexander-schranz]

There are 2 ways of getting this merged. First would be create a fork of the used postcss plugin based on existi compatible pull request here: madeleineostoja/postcss-hexrgba#33
Second one would be go to alternative plugin. Like the following but it does make the code a lot harder to read and requires a rewrite of all rgba usages currently https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-color-hex-alpha.

I personally would go with fork exist postcss-hexrgba package.

/cc @sulu/core-team

[niklasnatter]

There are 2 ways of getting this merged. First would be create a fork of the used postcss plugin based on existi compatible pull request here: madeleineostoja/postcss-hexrgba#33 Second one would be go to alternative plugin. Like the following but it does make the code a lot harder to read and requires a rewrite of all rgba usages currently https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-color-hex-alpha.

Looks like madeleineostoja/postcss-hexrgba#33 was merged a few hours ago, so we dont need to fork 🥳