[DOCS] Regenerate the class diagram in the README

[oliverklee]

The class diagram is (almost) unchanged to the output from tasuku43/mermaid-class-diagram, except for the kept direction LR.

This is in preparation for adding a script for auto-creating the class diagram in #1297.

[coveralls]

coverage: 57.935%. remained the same
when pulling adeb8fb on docs/update-class-diagram
into 674cfa0 on main.

[oliverklee]

Marking this as draft for now. I'll first reorder the classes in the diagram to make this PR here a bit smaller.

[JakeQZ]

It would be nice if the diagram had fewer criss-crossing paths. AI should be good at that, but seems to be vastly overrated :/

[JakeQZ]

The previous source for the diagram had entries like

URL --> "1" CSSString: url

whereas now we have

URL ..> CSSString: dependency

So we no longer identify the property that has the dependency (or whether it's as a single object, array, or whatever). Is there any reason for this change?

[oliverklee]

So we no longer identify the property that has the dependency (or whether it's as a single object, array, or whatever). Is there any reason for this change?

The old version of the generator which we used did not recognize associations at all. That's why I manually added those to the diagram, including the name of the corresponding property.

The current version of the generator does recognize associations, even though it only labels them as "dependency", but not with the name of the corresponding property.

[JakeQZ]

I spent a bit of time reordering the original 'relationships' section, after changing to the now-generated syntax, to conclude that there a quite a few differences there.

I think this needs three separate pre-patches so the diffs can be more clearly seen (along the lines of #1299):

1. Move class URL to be ASCII-sorted;
2. Change to use ..>, dependency and remove "*"/"1";
3. Reorder the relationships to be consistent with the generated order.

For reference, what I did for reviewing is on the branch at https://github.com/MyIntervals/PHP-CSS-Parser/tree/docs/class-diagram-review and includes all three of the above, which need to be split. And I may have made mistakes: there was a lot of cutting and pasting

[oliverklee]

I think this needs three separate pre-patches so the diffs can be more clearly seen

Makes sense, will do.