Added Wolfram Language extensions to the Mathematica section. I checked whether other languages have the same extensions I indroduced which is not the case.

Added a sample .wlt file for a Wolfram Unit Test

lib/linguist/languages.yml

@@ -1761,6 +1761,9 @@ Mathematica:
   - .ma
   - .nb
   - .nbp
+  - .wl
+  - .mt
+  - .wlt
   aliases:
   - mma
   ace_mode: text

samples/Mathematica/UnitTest.wlt

@@ -0,0 +1,17 @@
+BeginTestSection["Untitled-5"]
+
+VerificationTest[(* 1 *)
+	RotationMatrix[phi]
+	,
+	List[List[Cos[phi], Times[-1, Sin[phi]]], List[Sin[phi], Cos[phi]]]	
+]
+
+VerificationTest[(* 2 *)
+	Times[1, Power[Plus[a, Times[-1, a]], -1]]
+	,
+	ComplexInfinity
+	,
+	{Power::infy}
+]
+
+EndTestSection[]