PS: Add a test demonstrating missing a variable.

Author: MathiasVP

powershell/ql/test/library-tests/ast/Variables/test.ps1

@@ -0,0 +1,5 @@
+$x = 42
+$x
+
+[int]$y = 42
+$y

powershell/ql/test/library-tests/ast/Variables/variables.expected

@@ -0,0 +1 @@
+| test.ps1:1:1:1:2 | x | test.ps1:2:1:2:2 | x |

powershell/ql/test/library-tests/ast/Variables/variables.ql

@@ -0,0 +1,3 @@
+import powershell
+
+query predicate variables(Variable v, VarReadAccess va) { va.getVariable() = v }