Squash this commit once upstream zg has accepted a PR which updates for
recent zig

Some terminals (foot, ghostty) encode shift + space as CSI 32 ; 2 u when
using the kkp disambiguate flag. We need to handle this as a printable
character. Use the logic from vaxis (the go version), which checks if
the mods were shift only and the character is printable. Then we upper
case it, set the text and the shifted char

Change the core loop for handling of mouse events. We now do a layout
phase, which calls draw on the root widget. From here, we see if the
widget underneath the mouse has changed and, if so, send mouse_enter and
mouse_exit events, then do another layout, and then *finally* we render.

This fixes a case where the mouse hasn't moved, but the content of the
screen has changed. The hover state of any widget will be updated in the
second layout phase if the app indicates a redraw is necessary from the
mouse_enter and mouse_exit events.

The lower bound must be within the parent window

Implement explicit width hint extension, developed by kitty. When
both explicit width and mode 2027 are available, we default to explicit
width. Custom event loop authors will need to update their loops to add
support for this by setting the new capability value.

For simplicity, we don't actually add a flag in the parser for checking
between a cursor position and an F3 key. Instead, we send the cursor
home, then do an explicit width command, *then* check the cursor
position. If the cursor has moved - meaning the extension is supported -
we will see an F3 key with the shift modifier. The response will be
something like `\x1b[1;2R` which we parse as a shift+F3. But in the
loop, we check the flag if we have sent queries and handle this specific
event differently.

Reference: https://github.com/kovidgoyal/kitty/issues/8226

This adds an example demonstrating the use of the ScrollView and
ScrollBars widgets. It also includes keybindings to change how the child
widgets are laid out so you can see how that affects how the scroll bars
are rendered.

The content size estimates are deliberately wrong to demonstrate how
that affects the scroll bars. The value is intended to be modified by
whoever is testing the example.

This widget is intended to wrap a ScrollView widget and show vertical
and horizontal scroll bars as indicators of scroll position in the
ScrollView. It's recommended to provide the estimated content sizes
with as much accuracy as possible for the best user experience and
performance.

If estimated content sizes are not provided the scroll bar sizes and
positions will be estimated using the size of child arrays. This is not
perfect and will cause inconsistencies if the child widgets aren't all
the exact same heights.

The widget will render its children in a container that can be scrolled
both horizontally and vertically. The widget itself does not render any
scroll bars or other indicators of current scroll position.

Since this view is heavily based on the ListView widget it inherits the
same `cursor` functionality to show the current position of a selected
widget.

Known Issues
============

1. The view currently does not enforce a maximum width on the content to
be able to correctly figure out whether the content can still be
scrolled horizontally. This will cause the widget to draw beyond its
boundaries horizontally.
2. When the last widget rendered is taller than a single row the whole
widget will be drawn. This will cause the widget to draw beyond its
boundaries vertically.

Implement mouse and focus events in windows. Thanks @neurocyte for
locating this.

Fixes: #159

vaxis-aio reuses the handleEventGeneric function

`\x0A` was being parsed as an enter keypress. Distinguish this explicitly as a ctrl+j press.

Some improvements to WindowsTty. The init function will now catch and
propagate an error.InvalidHandle so that caller can catch/handle it.

In addition, I added packed structs for the input/output
console modes which makes it convenient to manage the bits and is what
zigwin32 generates for its bindings. I also made these newly added types
and wrapper functions public as they can be generally useful for terminal
applications.

It should be pretty safe to assume that posix.empty_sigset
is supported on most, if not all, posix systems. Individual
OSes that need a different default value may add a case to
the switch like macos.

This should open up support for most other posix systems.

closes #151