Add theme support, light theme, and edgeless light

sass/includes/_subscriptions-page.sass

@@ -0,0 +1,46 @@
+$_theme: () !default
+
+@use "sass:map"
+@use "forms" as forms
+@use "video-list-item" as *
+
+.subscriptions-page
+  padding: 40px 20px 20px
+  max-width: 900px
+  margin: 0 auto
+
+.subscriptions-video
+  @include subscriptions-video
+
+.no-subscriptions
+  text-align: center
+
+.channels-details
+  margin-bottom: 24px
+
+.channels-list
+  display: grid
+  grid-gap: 8px
+
+.channel-item
+  display: flex
+  align-items: center
+  text-decoration: none
+
+  .thumbnail
+    width: 40px
+    height: 40px
+    border-radius: 50%
+    margin-right: 8px
+
+  .name
+    font-size: 22px
+    color: map.get($_theme, "fg-main")
+
+@include forms.checkbox-hider("watched-videos-display")
+
+#watched-videos-display:checked ~ .video-list-item--watched
+  display: none
+
+.mark-watched
+  @include forms.single-button-form