Add WebVTT cue alignment feature

Author: foolip

features/webvtt-cue-alignment.yml

@@ -0,0 +1,8 @@
+name: WebVTT cue alignment
+description: The WebVTT cue alignment settings control which part of the cue is aligned with the given line and position. Cue alignment is set using `line` and `position` settings in WebVTT files or the `lineAlign` and `positionAlign` properties of `VTTCue` using JavaScript.
+spec:
+  - https://w3c.github.io/webvtt/#dom-vttcue-linealign
+  - https://w3c.github.io/webvtt/#dom-vttcue-positionalign
+compat_features:
+  - api.VTTCue.lineAlign
+  - api.VTTCue.positionAlign

features/webvtt-cue-alignment.yml.dist

@@ -0,0 +1,10 @@
+# Generated from: webvtt-cue-alignment.yml
+# Do not edit this file by hand. Edit the source file instead!
+
+status:
+  baseline: false
+  support:
+    firefox: "31"
+    firefox_android: "31"
+    safari: "14.1"
+    safari_ios: "14.5"