sh: Add make-and-enter directory function

`mcd` will, similarly to `md` create a directory and all the necessary
top-level directories but, unlike `md`, afterwards also enter the
created directory for the current shell.

sh/.config/sh/alias

@@ -40,6 +40,11 @@ alias ...="cd ../.."
 alias ~="cd ~"
 
 alias md="mkdir -p"
+mcd() {
+    mkdir -p "$@"
+    cd "$1" || exit 1
+}
+
 
 # clear my screen
 alias cl="clear"