Add hidden escape sequence
This adds support for the `hidden` escape sequence `\e[8m`, which will render the text as invisible. This has also raised a few questions about the rendering of foreground and background colors and their interaction with the different escape sequences. Previously, Alacritty has oriented itself after URxvt, which has some strange and unexpected behavior. The new implementation of color inversion is modeled after XTerm, which has a consistent pattern of always inverting the foreground and background colors. This should hopefully lead to less confusion for the user and a more consistent behavior. A full matrix showcasing the new way Alacritty inverses text can be found here: https://i.imgur.com/d1XavG7.png This fixes #1454 and fixes #1455.
Showing with 79 additions and 42 deletions