OSC 7 notify working directory support

[rzhw]

OSC 7 is an escape sequence to notify the terminal emulator of the program's current working directory. There is no formal spec for this. Efforts were made in freedesktop.org's terminal-wg, but these seem stalled.

However, OSC 7 is widely supported.

Here's macOS Sequoia's description of it:

Here's a summary of findings I made of wider adoption (trying to justify why an existing application should print OSC 7):

Terminal	Currently supported?
macOS Terminal	Yes
Gnome Terminal	Yes
KDE Konsole	Yes
iTerm2	Yes
JetBrains JediTerm	Yes
WezTerm	Yes
Kitty	Yes
Visual Studio Code	Yes
Vim	Yes
Neovim	Yes
Midnight Commander	Yes
Tmux	Yes
Emacs	Yes
Windows Terminal	No (Primarily due to WSL edge cases)
Alacritty	No

There also exist the related OSC 1337 proprietary to iTerm2, and OSC 633 proprietary to VSCode, and OSC 9;9 supported on Windows by ConEmu and Windows Terminal.

Not sure if it makes sense to support OSC 1337 and OSC 633, maybe it does make sense to support OSC 9;9 too?

I started work on a PR for just OSC 7, but it seems like to write unit tests charmbracelet/x/ansi also needs to support this, so I'll create this ticket first for referencing.