This removes the releases section to make the creation of new releases a
bit simpler.

Alacritty's description in the readme and manpage has always been a bit
overly aggressive in its marketing. This new updated text should more
accurately describe Alacritty's current state without pointlessly
agitating people.

Since Alacritty is now officially packaged by Fedora, it is no longer
necessary to provide this in the official repository.

This is only an update to the development version and does not represent
a stable release.

Since Alacritty should not be responsible for packaging and the
maintainers of the snap package have not kept it up to date, this
removes its configuration file.

Fixes #3628.

This implements a basic mode for navigating inside of Alacritty's
history with keyboard bindings. They're bound by default to vi's motion
shortcuts but are fully customizable. Since this relies on key bindings
only single key bindings are currently supported (so no `ge`, or
repetition).

Other than navigating the history and moving the viewport, this mode
should enable making use of all available selection modes to copy
content to the clipboard and launch URLs below the cursor.

This also changes the rendering of the block cursor at the side of
selections, since previously it could be inverted to be completely
invisible. Since that would have caused some troubles with this keyboard
selection mode, the block cursor now is no longer inverted when it is at
the edges of a selection.

Fixes #262.