Add CSS will-change (#1118)

This is a Baseline 2020 feature.

features/will-change.dist.yml

@@ -0,0 +1,26 @@
+# Generated from: will-change.yml
+# Do not edit this file by hand. Edit the source file instead!
+
+name: will-change
+description: "The `will-change` CSS property gives hints to the browser about expected changes to an element's scroll position, contents, or style. These hints allow browsers to optimize for upcoming style changes."
+spec: https://drafts.csswg.org/css-will-change-1/
+group: css
+usage_stats: https://chromestatus.com/metrics/css/timeline/popularity/445
+caniuse: will-change
+status:
+  baseline: high
+  baseline_low_date: 2020-01-15
+  baseline_high_date: 2022-07-15
+  support:
+    chrome: "36"
+    chrome_android: "36"
+    edge: "79"
+    firefox: "36"
+    firefox_android: "36"
+    safari: "9.1"
+    safari_ios: "9.3"
+compat_features:
+  - css.properties.will-change
+  - css.properties.will-change.auto
+  - css.properties.will-change.contents
+  - css.properties.will-change.scroll-position

features/will-change.yml

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+name: will-change
+description: "The `will-change` CSS property gives hints to the browser about expected changes to an element's scroll position, contents, or style. These hints allow browsers to optimize for upcoming style changes."
+spec: https://drafts.csswg.org/css-will-change-1/
+group: css
+usage_stats: https://chromestatus.com/metrics/css/timeline/popularity/445
+caniuse: will-change
+compat_features:
+  - css.properties.will-change
+  - css.properties.will-change.auto
+  - css.properties.will-change.contents
+  - css.properties.will-change.scroll-position