CSS Typed OM get property return types

[ophirbucai]

Narrow down return type of StylePropertyMapReadOnly.get() to match CSS Types OM specification. Properties now return their specific CSSStyleValue sub classes:

• CSSUnitValue
• CSSKeywordValue
• CSSTransformValue
• Default: CSSStyleValue

This change provides better type safety and autocompletion when working with computedStyleMap().

Changes:

• Added specific return types for common CSS properties in StylePropertyMap
• Maintained backwards compatibility with fallback to CSSStyleValue
• Included links to MDN documentation

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @saschanaz - if they write a comment saying "LGTM" then it will be merged.

[ophirbucai]

@microsoft-github-policy-service agree

[ophirbucai]

I realized that there are more type definitions such as:

• CSSImageValue
• CSSUnparsedValue
• CSSMathValue
  I've mapped all the properties listed in MDN and consolidated those into a couple of function overloads.

The process involved:

1. Querying MDN for all possible properties.
2. Testing each property with common values to reflect the CSSStyleValue subclasses:

[
    /* Units: */
    '10px', 
    '10%', 
    /* Keywords: */ 
    'auto', 
    'none',
    /* Math: */
    'calc(100% - 20px)',
    /* Style: */
    'rgb(255,0,0)',
    /* Image: */
    'url("test.jpg")',
    /* Transform: */
    'matrix(1, 0, 0, 1, 0, 0)'
]

3. Grouping properties by their return type combinations.
4. Adding relevant MDN references for each group

Hope it helps people use computedStyleMap().