feat: implemented pipes and redirects + background operator

cmd.h

@@ -29,6 +29,8 @@ typedef struct CommandList {
 typedef struct Chain {
   CommandList commands;
   bool runInBackground;
+  char *in;
+  char *out;
 } Chain;
 
 
@@ -36,6 +38,7 @@ void freeCommand(Command cmd);
 void freeChain(Chain chain);
 
 Command buildCommand(List *lp);
+void addRedirect(List *lp, Chain *chain);
 Chain buildChain(List *lp);
 
 void executeChain(Chain chain, int* status);