Add CSS gap decorations feature (#3027)

Author: captainbrosset

features/gap-decorations.yml

@@ -0,0 +1,21 @@
+name: Gap decorations
+description: The `column-rule` and `row-rule` CSS properties display decorative lines between columns and rows of a flex, grid, or multi-column layout. The `rule-break`, `rule-outset`, and `rule-paint-order` properties control the appearance of these lines.
+spec: https://drafts.csswg.org/css-gaps-1/
+group:
+  - grid
+  - flexbox
+  - multi-column
+# No BCD keys yet, expecting the following keys:
+
+# - css.properties.column-rule
+# - css.properties.row-rule
+# And equivalend long-hands.
+
+# - css.properties.rule-break
+# - css.properties.row-rule-break
+# - css.properties.column-rule-break
+# - css.properties.rule-outset
+# - css.properties.row-rule-outset
+# - css.properties.column-rule-outset
+
+# - css.properties.rule-paint-order

features/gap-decorations.yml.dist

@@ -0,0 +1,6 @@
+# Generated from: gap-decorations.yml
+# Do not edit this file by hand. Edit the source file instead!
+
+status:
+  baseline: false
+  support: {}