feat: add container at rule

[Netail]

Description

Add @container at rule

Motivation

VSCode not correctly syntax hightlighting

Additional details

https://developer.mozilla.org/en-US/docs/Web/CSS/@container
https://drafts.csswg.org/css-conditional-5/#container-rule

Related issues and pull requests

[skyclouds2001]

Suggested change

	"syntax": "@container <container-condition># {\n <block-contents>\n}",
	"syntax": "@container <container-condition># {\n <block-contents>\n}",

the syntax need to add to syntaxes.json if it is not existed in that file

e.g. #835

[Netail]

Applied your feedback, thanks :)

[skyclouds2001]

Currently sone at-rule includes its interface and inherited interface, while most are not. This may need desicion, but it OK to not modify this at present.

In docs:

• interfaces (array of strings): These are the CSSOM interfaces that belong to the at-rule.

For this reason, personally I think only CSSContainerRule should be represented.

Wonder if you have other opinions:

[Netail]

Mhm, I just followed some of the other at-rules which included the top 2 interfaces as well as their own

[skyclouds2001]

yes, it is true, so I mean what do you think of this case? If not sure, you could simply keep it.

[Netail]

I don't mind, let's keep it for now I guess

[skyclouds2001]

I think twice, and I think we should not keep inherit interfaces.

i. currently only three cases list inherit interfaces (including one that no list direct interface), while nine cases only list direct interface
ii. the inherit info is a API feature, which is better to maintain at inheritance.json
iii. as per the docs, the interface belong to the at-rule, mostly I think this is only the direct interface

see also #856