Move os layer to be part of the core

src/core/os/shell/termcolour/termcolour.c

@@ -0,0 +1,15 @@
+#include "termcolour.h"
+#include "terminal_colours.h"
+
+void wapp_shell_termcolour_print_text(Str8RO *text, TerminalColour colour) {
+  if (colour < WAPP_TERM_COLOUR_FG_BLACK || colour > WAPP_TERM_COLOUR_FG_BR_WHITE) {
+    return;
+  }
+
+  print_coloured_text(text, colour);
+}
+
+void wapp_shell_termcolour_clear_colour(void) {
+  Str8RO empty = wapp_str8_lit_ro("");
+  print_coloured_text(&empty, WAPP_TERM_COLOUR_CLEAR);
+}