[Feature] translate rich text blocks

[sargreal]

This adds experimental support for translating the blocks editor (fixes #401). The current implementation is very rudimentary.

Things to consider before merging:

• How to handle images better? The current way of creating a cache does not delete any images and may become a memory leak in large applications. But it is not clear when the cache may be deleted
• How to handle code better? In the current state, DeepL may just translate the code and in the process also remove any line breaks.
• Is it worth launching this feature in an experimental state, since we currently do not have the resources to fix bugs?

[codecov]

Codecov Report

Attention: Patch coverage is 65.47619% with 29 lines in your changes are missing coverage. Please review.

Project coverage is 47.77%. Comparing base (0823a66) to head (3cb37ca).

Files	Patch %	Lines
plugin/server/services/format.js	68.57%	9 Missing and 13 partials ⚠️
providers/deepl/lib/index.js	50.00%	2 Missing and 2 partials ⚠️
providers/libretranslate/lib/index.js	50.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #402      +/-   ##
==========================================
+ Coverage   45.95%   47.77%   +1.81%     
==========================================
  Files          47       47              
  Lines         866      942      +76     
  Branches      187      211      +24     
==========================================
+ Hits          398      450      +52     
- Misses        310      322      +12     
- Partials      158      170      +12     

Flag	Coverage Δ
unittests	47.77% <65.47%> (+1.81%)	⬆️

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[layaxx]

I don't think we should merge this into main right now. At most as an opt-in via a next release or something like that.
I agree that the handling of code (both blocks and inline) is not great, not sure what to do here. Same with the clearing of the img cache

[layaxx]

Again:
is it block or blocks?
cf. playground/config/plugins.js and root-level README

[layaxx]

i think the inverse conversion back to blocks format is missing.

[layaxx]

translation of blocks-article type via libretranslate fails, not sure if this is the (only) reason

[bieblebrox]

Is there any progress on this? Would be a very useful feature to have.

[sargreal]

I don't think we should merge this into main right now. At most as an opt-in via a next release or something like that. I agree that the handling of code (both blocks and inline) is not great, not sure what to do here. Same with the clearing of the img cache

I actually realised that code is currently handled the same with markdown and other html stuff. I believe that this should be made into a separate "known" bug for now.