Mainly bug fixes, with some styling scripts added.

New Features

• add general.clear_screen_after_execution, which is useful when chafa image flash back after command execution
• add interface.header_concatenate option, which allows for concatenation (be in the same line) between interface header_cmd output and interface.header
• render header_cmd output through rustyline editor, so that chafa image can coexist with with the editing line
• better flow control for the overall process
• helper scritps for styling

Bug fixes

• fix general.clear_screen_after_execution not working
• fix empty header_cmd printing an uneccessary line
• fix chafa-text.sh not rendering paddings in chafa symbol mode
• fix header_cmd not printed right in loop_mode
• streamlining codes