feat(ui): LESS Integration

#15-Create-a-default-theme-with-Less- (#23)
Added LESS and created a light mode

Co-authored-by: LQ63 <lkhermann@web.de>
Reviewed-on: #23
Reviewed-by: Janis <janis-e@gmx.de>
Co-authored-by: lq64 <lq@blackhole.local>
Co-committed-by: lq64 <lq@blackhole.local>

knockoutwhistweb/app/assets/stylesheets/main.less

@@ -1,5 +1,7 @@
+@import "light-mode.less";
 body {
-    background-image: url("/assets/images/background.png");
+    background-image: @background-image;
+    background-size: 100vw 100vh;
 }
 
 html, body {
@@ -15,7 +17,7 @@ html, body {
 }
 
 #sessions a, h1, p {
-    color: white;
+    color: @color;
     font-size: 40px;
     font-family: Arial;
 }
@@ -81,10 +83,10 @@ html, body {
     flex-direction: column;
     align-items: center;
     height: 0%;
-}
-#nextPlayers p {
-    margin-top: 0px;
-    margin-bottom: 0px;
+    p {
+        margin-top: 0px;
+        margin-bottom: 0px;
+    }
 }
 #invisible {
     visibility: hidden;

project/plugins.sbt

@@ -3,4 +3,6 @@ addSbtPlugin("org.foundweekends.giter8" % "sbt-giter8-scaffold" % "0.18.0")
 
 addSbtPlugin("org.scoverage" % "sbt-scoverage" % "2.2.1")
 addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "2.3.0")
-addSbtPlugin("org.scoverage" % "sbt-coveralls" % "1.3.1")
+addSbtPlugin("org.scoverage" % "sbt-coveralls" % "1.3.1")
+
+addSbtPlugin("com.typesafe.sbt" % "sbt-less" % "1.1.2")