test(Tcl): add shebang source files for regression test

CI reported FileNotFoundError for Tcl/{tclsh,expect,wish}_shebang in
tests/syntax-tests/source/Tcl/. The highlighted files existed but the
source files had been omitted, so create_highlighted_versions.py had
nothing to read from.

Source files match the shebang regression test inputs at
tests/examples/regression_tests/issue_3647_*.

tests/syntax-tests/source/Tcl/wish_shebang

@@ -0,0 +1,5 @@
+#!/usr/bin/wish
+# Tk script detected via wish shebang
+package require Tk
+button .b -text "Click" -command {puts "clicked"}
+pack .b