Play videos, more options

Most notable in this release are

• timg can now also play videos (compile-time choice).
• A manpage now makes this a 'proper' tool.
• A few more options relevant for video playing as well as centering images with -C or switching off antialiasing with -a. Probably a few more I forgot.
• The character to use to display pixels can now be changed via an environment variable.
• Some silly performance improvements (so we could show 3000fps if the terminal would be able to deal with it...).

Transparent image background; fzf preview

• Allow to choose the background color, or checkerboard pattern, for images with transparent background.
• more command line options, e.g. choice of hiding the cursor.

More scrolling options, faster output

• Improved set of scrolling in various directions
• Generally a little more optimized

First public release.

Initial release of the timg Terminal Image Viewer