docs(icon): add new icon system ADR

[roberttran-cc]

Fixes #683.

Looking forward your feedback! 😇

I tried to avoid adding too much details, to keep the document readable, but some parts may be lacking. 😵

Question 1
I decided to put @florian-sanders-cc's a11y part inside this ADR but, after some thoughts, should we do like the toaster's ADRs and split the content? I'm not sure it is relevant in this case, WDYT?

Question 2 (from @florian-sanders-cc)
Some headings proposals, WDYT bis? Details in his answer.

TO DO after review and before merging :

• update the date

[florian-sanders-cc]

Hey !

Really great work 🚀 , you managed to deliver a synthetic explanation for tricky subject, it was very interesting to read 👍
Since you managed to keep your part fairly short, I think we could keep a single ADR with the accessibility part inside, as it is right now but let's see what others think 👍 (one way or another, I'm ok with it 😉

I added suggestions, mainly rewording (which is quite subjective as always so really it's up to you in most cases 😉).
About the headings in the "The problem" section, I wonder if we could use headings that describe the problems a little bit more like:
"As static assets with no backing icon library" => "(Lack of) Standardization and optimization"
"As image tags" => "(Lack of) Customization"
"And more" => "(Lack of) Compatibility"

Not sure the "Lack of" is necessary because we're in "The problem" (might need to become "The problems" now that I think about it).
WDYT?

Also, I remember you explained why you went for inline <svg> elements instead of sprites (not sure this is the right terminology, sorry if not) during a meeting.

Should we say more about this subject in this ADR? I thought it was an interesting subject and it could be great to write down the downsides that made us choose inline <svg> instead. (I say that but I realise it's not an easy subject ahah)

[hsablonniere]

Impressive work @roberttran-cc 👏 !!!

I'm not sure how to write it but in the context or the problem section, we could mention that a few shortcuts were made at the beginning while it was a one-person project. Defining a robust icon strategy was one of them. Now that we have a need we can and need to address this.

(Aside note, E2E tests is also one of those shortcuts)

[pdesoyres-cc]

Awesome work. Well done.

[Galimede]

LGTM, gg that's impressive 👏 🤯

[hsablonniere]

I decided to put @florian-sanders-cc's a11y part inside this ADR but, after some thoughts, should we do like the toaster's ADRs and split the content? I'm not sure it is relevant in this case, WDYT?

The ADR is long but I don't see it as a problem. I think I prefer to have the a11y part along with the rest. So no split for me.

Some headings proposals, WDYT bis? Details in his answer.

• I'm not sure "the problem" needs to be plural as it's a very general title.
• I like @florian-sanders-cc suggestions for headings rework
  • I prefer the simple version without "lack of"
    • "Standardization and optimization"
    • "Customization"
    • "Compatibility"