CI: Image optimization

[M123-dev]

Problem

We got some svg optimization from @lsaudon in #2414.

It would be great if we could automate and expand it beyond svgs only.

My preference would be ImgBot which could also be interesting for other repos as well. Would you have a look at this @teolemon

Part of

• Refactoring (tracker) #2528

[monsieurtanuki]

My 2 cents...

I'm not a big fan of systematic optimization

• they have side-effects (fix: Revert "refactor: Avoid unused parameters (#2407)" #2418, perf: Optimize SVG files #2414 (comment))
• so far they are not tested (what about goldens test for SVGs?)
• I didn't see any evidence of the gain in space (would be easy to measure) and performances (less easy)
• in the case of SVG optim, I don't know what the source SVG files were (if they were those in assets/ they were already downgraded optimized files)
• it distracts us from more important issues, especially now that the app is live

TL;DR
If it is tested, if it does optimize the app, if it's fast to code and easy to maintain, why not.

[AshAman999]

so far they are not tested (what about goldens test for SVGs?)

Ran test on my fork for IMG bot and all test were passing ,doesn't seem to have any breaker for now to stop it from being implemented in our project
AshAman999#1

[monsieurtanuki]

@AshAman999 I'm not sure the Smoothie tests include the correct display of the 233 SVG files (with the flutter limitations regarding SVG display). For PNG I assume we're safer and that flutter displays them correctly.

In addition to optimization, an added value would be to get the original files from the server and to put them in assets/. Cf. #1963.