build: add stylelint rule for eof newlines (#5832)

src/demo-app/checkbox/checkbox-demo.scss

@@ -1,4 +1,3 @@
 .demo-checkboxes {
   margin: 8px 0;
-  
-}
+}

src/demo-app/expansion/expansion-demo.scss

@@ -1,4 +1,4 @@
 .md-expansion-demo-width {
   width: 600px;
   display: block;
-}
+}

src/demo-app/menu/menu-demo.scss

@@ -10,4 +10,4 @@
   .end-icon {
     align-items: flex-end;
   }
-}
+}

src/demo-app/progress-bar/progress-bar-demo.scss

@@ -13,4 +13,4 @@
 
 .demo-progress-bar-controls {
   margin: 10px 0;
-}
+}

src/demo-app/progress-spinner/progress-spinner-demo.scss

@@ -10,4 +10,4 @@
 
 .demo-progress-spinner-controls {
   margin: 10px 0;
-}
+}

src/lib/core/style/_form-common.scss

@@ -9,4 +9,4 @@ $mat-underline-disabled-background-image:
   background-image: $mat-underline-disabled-background-image;
   background-size: 4px 1px;
   background-repeat: repeat-x;
-}
+}

src/lib/tabs/tab-header.scss

@@ -86,4 +86,4 @@
 
 .mat-tab-labels {
   display: flex;
-}
+}

src/lib/tabs/tab-nav-bar/tab-nav-bar.scss

@@ -29,4 +29,4 @@
 // Styling for the ink bar that displays near the activated anchor
 .mat-ink-bar {
   @include ink-bar;
-}
+}

stylelint-config.json

@@ -72,6 +72,7 @@
     "selector-pseudo-element-colon-notation": "double",
     "selector-pseudo-element-no-unknown": true,
     "selector-type-case": "lower",
-    "selector-max-id": 0
+    "selector-max-id": 0,
+    "no-missing-end-of-source-newline": true
   }
 }