add dev/TODO

dev/TODO

@@ -0,0 +1,21 @@
+- working history (rl_* functions?)
+	- '<<' with history?
+- finding commands
+	- built-in commands
+	- relative/absolute paths
+- signals
+	- ^C, ^D, ^\
+- variables
+	- normal variables
+	- environment variables
+	- $?
+- pipes
+	- no calls (like `$ < input_file > output_file`)
+- builtins:
+	- echo		(with option -n)
+	- cd [path]
+	- pwd		(with no options)
+	- export	(with no options)
+	- unset		(with no options)
+	- env		(with no options or arguments)
+	- exit		(with no options)