[MISC]: Amended TODO file
[FEATURE]: Added find_env_var(), added export-var builtin shell command for exporting built in variables to the system environment. Amended export_sys_env_var() to use new find_env_var() function to find variable by name instead of passing a pointer.
[FEATURE]: Added command history using libtecla. Amended parse() to add history after strip_newline(). Added DEFAULT_HISTORY_MEM macro.
[FEATURE]: Added super useful cprint_msg() to print formatted text to a stream along with terminal escape codes for various colors. Amended TODO.