Revert "add parallel convert"

This reverts commit 6ee682ae1c41bfd64968d71334d72b52c8d29ca3.

add parallel convert

Add some convert to fixed the lint issue

add main test case

add convert test case

refactor the convert package

Fixed a slice allocate issue

Rewrite the go docs

fixed the comment

add colored the asicc output

Add the method to fit the screen

add new method to convert a image from filename directly

add convert package to convert a image to ascii matrix