fix: char can be signed or unsigned depending on platform, make it ex…

…plicit

chars can be signed or unsigned by default, as we expect signed here, make it
explicit.

Fixes error on arm64:

./../vtools/dialogs/tools/dialogtool.h:100:45: error: enumerator value ‘-7’ is outside the range of underlying type ‘char’
  100 | enum class DialogPosition : char {Offset = -7, BottomRight, BottomLeft, Center, TopRight, TopLeft};
      |

src/libs/vtools/dialogs/tools/dialogtool.h

@@ -97,7 +97,7 @@ class QPlainTextEdit;
 class VAbstractTool;
 
 enum class FillComboBox : char {Whole, NoChildren};
-enum class DialogPosition : char {Offset = -7, BottomRight, BottomLeft, Center, TopRight, TopLeft};
+enum class DialogPosition : signed char {Offset = -7, BottomRight, BottomLeft, Center, TopRight, TopLeft};
 
 /**
  * @brief The DialogTool class parent for all dialog of tools.