[css-syntax-3][css-cascade][css-conditional] Missing definition of `<declaration>`

[SebastianZ]

CSS Cascade 4 and 5 as well as CSS Conditional 3 and 5 refer to a <declaration> type, which is currently not defined.

That should probably be added to CSS Syntax 3, where the term "declaration" is already defined.

@tabatkins @SimonSapin

Sebastian

[svgeesus]

Syntax 3 defines

• declaration, in § 5.2
• <declaration-list>, in § 7.1
• <declaration-rule-list>, in § 7.1
• <declaration-value>, in § 7.2

but not <declaration>