Map snap-event WPTs to web-features

web-features[1] is an effort to build a shared catalog of features of the web platform.

This patch adds some of the necessary configuration to ensure that
snap events are represented in web-features. Snap Events have been
added[2] to the web-features repository as
scroll-snap-events.

[1] https://github.com/web-platform-dx/web-features
[2] web-platform-dx/web-features@e4c5805

Bug: 365784987
Change-Id: I31c901305dd72fde21a5d5cf1176604fbaa91bde
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5851064
Commit-Queue: David Awogbemila <awogbemila@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1382338}

css/css-scroll-snap-2/WEB_FEATURES.yml

@@ -0,0 +1,5 @@
+features:
+- name: scroll-snap-events
+  files:
+  - snap-events-with-pseudo-target.tentative.html
+  - snapevents-at-document-bubble-to-window.html

css/css-scroll-snap-2/scrollsnapchange/WEB_FEATURES.yml

@@ -0,0 +1,3 @@
+features:
+- name: scroll-snap-events
+  files: "**"

css/css-scroll-snap-2/scrollsnapchanging/WEB_FEATURES.yml

@@ -0,0 +1,3 @@
+features:
+- name: scroll-snap-events
+  files: "**"