fix(overlay): ensure container covers entire screen (#1634)

Author: jelbourn

src/lib/core/overlay/_overlay.scss

@@ -18,8 +18,8 @@
     // The container should be the size of the viewport.
     top: 0;
     left: 0;
-    height: 100%;
-    width: 100%;
+    height: 100vh;
+    width: 100vw;
     z-index: $md-z-index-overlay-container;
   }
 

stylelint-config.json

@@ -19,7 +19,7 @@
 
     "unit-case": "lower",
     "unit-no-unknown": true,
-    "unit-whitelist": ["px", "%", "deg", "ms", "em", "vh"],
+    "unit-whitelist": ["px", "%", "deg", "ms", "em", "vh", "vw"],
 
     "value-list-comma-space-after": "always-single-line",
     "value-list-comma-space-before": "never",