Reintroduce C++ support and add usage tests for C++ (#4)

Reviewed-on: #4
Co-authored-by: Abdelrahman <said.abdelrahman89@gmail.com>
Co-committed-by: Abdelrahman <said.abdelrahman89@gmail.com>

src/core/os/shell/commander/commander.h

@@ -11,10 +11,18 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#ifdef WAPP_PLATFORM_CPP
+BEGIN_C_LINKAGE
+#endif // !WAPP_PLATFORM_CPP
+
 #define CMD_NO_EXIT(ERR) ((CMDResult){.exited = false, .exit_code = EXIT_FAILURE, .error = ERR})
 
 CMDResult wapp_shell_commander_execute(CMDOutHandling out_handling, Str8 *out_buf, const Str8List *cmd);
 
 external CMDError get_output_status(FILE *fp, i32 *status_out);
 
+#ifdef WAPP_PLATFORM_CPP
+END_C_LINKAGE
+#endif // !WAPP_PLATFORM_CPP
+
 #endif // !COMMANDER_H