added The Witness (#472)

"Testing" because it only works with low graphic settings

Applications/Games/The Witness/Steam/script.js

@@ -0,0 +1,8 @@
+include(["Engines", "Wine", "QuickScript", "SteamScript"]);
+
+new SteamScript()
+    .name("The Witness")
+    .editor("Thekla, Inc.")
+    .author("Plata")
+    .appId(210970)
+    .go();

Applications/Games/The Witness/Steam/script.json

@@ -0,0 +1,7 @@
+{
+	"scriptName": "Steam",
+	"compatibleOperatingSystems": ["LINUX"],
+	"testingOperatingSystems": ["LINUX"],
+	"free": false,
+	"requiresPatch": false
+}

Applications/Games/The Witness/application.json

@@ -0,0 +1,4 @@
+{
+	"name":	"The Witness",
+	"description": "You wake up, alone, on a strange island full of puzzles that will challenge and surprise you.<br><br>You don't remember who you are, and you don't remember how you got here, but there's one thing you can do: explore the island in hope of discovering clues, regaining your memory, and somehow finding your way home.<br><br>The Witness is a single-player game in an open world with dozens of locations to explore and over 500 puzzles. This game respects you as an intelligent player and it treats your time as precious. There's no filler; each of those puzzles brings its own new idea into the mix. So, this is a game full of ideas."
+}