LibWeb/CSS: Parse the tab-size property

Author: https://github.com/kostyafarber
Commit: 68a28ff33a
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1560
Reviewed-by: https://github.com/AtkinsSJ ✅

Tests/LibWeb/Text/expected/css/getComputedStyle-print-all.txt

@@ -31,6 +31,7 @@ quotes: auto
 stroke: none
 stroke-opacity: 1
 stroke-width: 1px
+tab-size: 8
 text-align: start
 text-anchor: start
 text-decoration-line: none
@@ -117,7 +118,7 @@ grid-row-start: auto
 grid-template-areas: 
 grid-template-columns: 
 grid-template-rows: 
-height: 2023px
+height: 2040px
 inline-size: auto
 inset-block-end: auto
 inset-block-start: auto