[Glitch] Refactor scss

Port f691afaae9 to glitch-soc

app/javascript/flavours/glitch/styles/variables.scss

@@ -31,6 +31,11 @@ $ui-highlight-color: $classic-highlight-color !default;        // Vibrant
 // Language codes that uses CJK fonts
 $cjk-langs: ja, ko, zh-CN, zh-HK, zh-TW;
 
+// Variables for components
+$media-modal-media-max-width: 100%;
+// put margins on top and bottom of image to avoid the screen covered by image.
+$media-modal-media-max-height: 80%;
+
 // Avatar border size (8% default, 100% for rounded avatars)
 $ui-avatar-border-size: 8%;