chore: Dark Phoenix selected file changes

Author: abose

src/styles/brackets.less

@@ -1471,14 +1471,15 @@ a, img {
     background: @bc-sidebar-selection;
     border-top: none;
     border-bottom: none;
+    border-left: none;
     box-sizing: border-box;
     height: 23px;
     width: 100%;
     position: absolute;
 }
 
 .sidebar-selection-extension, .filetree-selection-extension {
-    background: @bc-sidebar-selection;
+    background: transparent;
     border-top: none;
     border-bottom: none;
     box-sizing: border-box;

src/styles/brackets_core_ui_variables.less

@@ -150,7 +150,7 @@
 
 // Sidebar
 @bc-sidebar-bg:                 #252525;
-@bc-sidebar-selection:          #404448;
+@bc-sidebar-selection:          rgba(90, 140, 255, 0.18);
 
 // images
 @button-icon:                   "images/find-replace-sprites.svg";
@@ -263,7 +263,7 @@
 
 // Sidebar
 @dark-bc-sidebar-bg:                 #252525;
-@dark-bc-sidebar-selection:          #404448;
+@dark-bc-sidebar-selection:          rgba(90, 140, 255, 0.18);
 
 // Plugin panel
 @plugin-panel-bg:                    #252525;