Feature request: Add unitless number properties data

[lifeiscontent]

Summary

It would be helpful to have a machine-readable list of CSS properties that accept unitless <number> or <integer> values (where units like px should not be added).

Use Case

CSS-in-JS libraries need to know which properties accept raw numbers without units. For example:

• opacity: 0.5 (unitless)
• z-index: 10 (unitless)
• flex-grow: 2 (unitless)
• line-height: 1.5 (unitless)

vs properties that need units:

• width: 100 → width: 100px
• margin: 10 → margin: 10px

Current State

The syntax field shows <number> or <integer> but doesn't clearly indicate whether the property is "unitless" in the sense that numeric values should NOT have units appended.

Proposed Enhancement

Add a unitless boolean field or similar indicator to properties that accept bare numbers:

{
  "name": "opacity",
  "syntax": "<alpha-value>",
  "unitless": true,
  ...
}

Or alternatively, a separate list of unitless properties.

Affected Properties

Common unitless properties include:

• opacity, fill-opacity, stroke-opacity, flood-opacity, stop-opacity
• z-index, order
• flex-grow, flex-shrink
• line-height (when unitless)
• font-weight (numeric values)
• orphans, widows
• column-count
• tab-size (when specifying character count)
• And more...