Update changelog.

Documentation: Bump sphinx version and update copyright year.

Set minimum Python version to 3.8.

Documentation: Format changelog to use Restructured text literals for…

… code-related references.

Update version to 0.8.1.

Lock deck once when updating key images in Tiled Image example script.

Bump version to 0.7.3.

Bump version to 0.7.2 so that the new documentation can be shown to n…

…ew users by default.

Bump version to 0.7.1.

Update documentation to refer to new HID backend transport.