chore(editor): port theme file from theme-default

scss/editor/_theme.scss

@@ -1 +1,62 @@
-@import "~@progress/kendo-theme-default/scss/editor/theme";
+@include exports("editor/theme") {
+
+    $editor-overlay-background: #000 !default;
+
+    .k-editor {
+        @include appearance( panel );
+
+        .k-editor-toolbar {
+            @include appearance( toolbar );
+        }
+        .k-editable-area {}
+    }
+
+    .k-overlay {
+        background-color: $editor-overlay-background;
+    }
+
+    // sass-lint:disable class-name-format
+    .editorToolbarWindow.k-header.k-window-content {
+        @include appearance( header );
+    }
+    // sass-lint:enable class-name-format
+    // sass-lint:disable class-name-format
+    .k-editor .k-editor-toolbar-wrap,
+    .k-ct-popup .k-editor-toolbar,
+    .editorToolbarWindow.k-header.k-window-content {
+        a.k-tool {
+            @include appearance( button );
+            border-width: 0;
+            background-image: none;
+            background-color: transparent;
+
+            &:hover,
+            &.k-state-hover {
+                @include appearance( hovered-button );
+                text-decoration: none;
+            }
+
+            &:active,
+            &.k-state-active {
+                @include appearance( pressed-button );
+                text-decoration: none;
+            }
+
+            &.k-state-selected {
+                @include fill( $selected-text, $selected-bg, $selected-border, none );
+            }
+        }
+        .k-tool-group {
+            border-color: $border-color;
+        }
+    }
+    // sass-lint:enable class-name-format
+
+
+    // Overflow anchor
+    .k-editor-toolbar .k-overflow-anchor {
+        padding: $toolbar-padding-y;
+        width: calc( #{$toolbar-inner-calc-size} );
+        height: calc( #{$toolbar-inner-calc-size} );
+    }
+}