global nav-bar-size css variable

src/App/styles.less

@@ -10,6 +10,7 @@
     --landscape-shape-ratio: 0.5625;
     --poster-shape-ratio: 1.464;
     --scroll-bar-width: 6px;
+    --nav-bar-size: 3.2rem;
     --focus-outline-size: 2px;
     --color-facebook: #4267b2;
     --color-twitter: #1DA1F2;

src/common/NavBar/styles.less

@@ -1,5 +1,4 @@
 .nav-bar-container {
-    --nav-bar-size: 3.2rem;
     display: flex;
     flex-direction: row;
     align-items: center;

src/common/Toast/styles.less

@@ -1,5 +1,4 @@
 .toast-container {
-    --nav-bar-size: 3.2rem;
     position: absolute;
     top: var(--nav-bar-size);
     right: 0;